According to Quran when Allah called Moses in heavens to give him the scripture, his people started worshipping a calf.

2:51 And [recall] when We made an appointment with Moses for forty nights. Then you took [for worship] the calf after him, while you were wrongdoers.

When Moses returned to earth Allah commanded people of Moses to kill each other (those who did not worship the calf killed those who worshipped it).

2:54 And [recall] when Moses said to his people, “O my people, indeed you have wronged yourselves by your taking of the calf [for worship]. So repent to your Creator and kill yourselves. That is best for [all of] you in the sight of your Creator.” Then He accepted your repentance; indeed, He is the Accepting of repentance, the Merciful.

Tafseer Ibn Kathir
An-Nasa’i, Ibn Jarir and Ibn Abi Hatim recorded Ibn `Abbas saying, “Allah told the Children of Israel that their repentance would be to slay by the sword every person they meet, be he father or son. They should not care whom they kill. Those were guilty whom Musa and Harun were not aware of their guilt, they admitted their sin and did as they were ordered. So Allah forgave both the killer and the one killed.” This is part of the Hadith about the trials that we will mention in Surat Ta Ha, (20) Allah willing.Ibn Jarir narrated that Ibn `Abbas said, “Musa said to his people, ﴿فَتُوبُواْ إِلَى بَارِئِكُمْ فَاقْتُلُواْ أَنفُسَكُمْ ذَلِكُمْ خَيْرٌ لَّكُمْ عِندَ بَارِئِكُمْ فَتَابَ عَلَيْكُمْ إِنَّهُ هُوَ التَّوَّابُ الرَّحِيمُ﴾ (“So turn in repentance to your Creator and kill each other (the innocent kill the wrongdoers among you), that will be better for you with your Creator.” Then He accepted your repentance. Truly, He is the One Who accepts repentance, the Most Merciful.) Allah ordered Musa to command his people to kill each other. He ordered those who worshipped the calf to sit down and those who did not worship the calf to stand holding knives in their hands. When they started killing them, a great darkness suddenly overcame them. After the darkness lifted, they had killed seventy thousand of them. Those who were killed among them were forgiven, and those who remained alive were also forgiven.”

Tafsir Ibn Abbas
Allah then mentioned the story of Moses with his people, saying: (And when Moses said unto his people: O my people! Ye have wronged yourselves) harmed yourselves (by your choosing of the calf) by worshipping the calf; and when Moses was then asked what to do, he said to them: (so turn in penitence to your Creator), again they asked him how to turn in penitence to Allah, and he said: (and kill (the guilty) among yourselves) let those who did not worship the calf kill those who worshipped it. (That) penitence and killing (will be best for you with your Creator and He will relent towards you) He will forgive you. (Lo! He is the Relenting) towards the penitent, (the Merciful) towards any that die repentant.

Tafseer Al-Jalalayn
And when Moses said to his people, those who worshipped the calf, ‘My people, you have done wrong against yourselves by your taking the [golden] calf, for a god; now turn to your Creator, away from that worship [of the calf] and slay one another, that is, let the innocent of you slay the guilty; That, slaughter, will be better for you in your Creator’s sight’, who made it easier for you to accomplish this and sent down a dark cloud over you, so that none of you was able to see the other and show him mercy, such that almost seventy thousand of you were killed; and He will turn to you [relenting], before your [turning in] repentance; truly He is the Relenting, the Merciful.

How is it different from some Hindu Gods or Goddesses who demanded human blood as sacrifice for blessings ?

After reading the following verses of Quran can you still believe Allah is the most merficul one ?

40:71-72When the shackles are around their necks and the chains; they will be dragged in boiling water; then in the Fire they will be filled [with flame].

22:19-21 – These are two adversaries who have disputed over their Lord. But those who disbelieved will have cut out for them garments of fire. Poured upon their heads will be scalding water; By which is melted that within their bellies and [their] skins ; And for [striking] them are maces of iron.

4:56 – Indeed, those who disbelieve in Our verses – We will drive them into a Fire. Every time their skins are roasted through We will replace them with other skins so they may taste the punishment. Indeed, Allah is ever Exalted in Might and Wise.

56:92-94 – But if he was of the deniers [who were] astray; Then [for him is] accommodation of scalding water; And burning in Hellfire

98:6 Indeed, they who disbelieved among the People of the Scripture and the polytheists will be in the fire of Hell, abiding eternally therein. Those are the worst of creatures

Sahih Muslim, Book 019, Number 4366
It has been narrated by ‘Umar b. al-Khattab that he heard the Messenger of Allah (may peace be upon him) say: I will expel the Jews and Christians from the Arabian Peninsula and will not leave any but Muslim.

Sahih al-Bukhari, Volume 3, Book 39, Number 531
Narrated Ibn ‘Umar:
Umar expelled the Jews and the Christians from Hijaz. When Allah’s Apostle had conquered Khaibar, he wanted to expel the Jews from it as its land became the property of Allah, His Apostle, and the Muslims. Allah’s Apostle intended to expel the Jews but they requested him to let them stay there on the condition that they would do the labor and get half of the fruits. Allah’s Apostle told them, “We will let you stay on thus condition, as long as we wish.” So, they (i.e. Jews) kept on living there until ‘Umar forced them to go towards Taima’ and Ariha’.

Sahih al-Bukhari, Volume 4, Book 52, Number 288
Narrated Said bin Jubair:
Ibn ‘Abbas said, “Thursday! What (great thing) took place on Thursday!” Then he started weeping till his tears wetted the gravels of the ground . Then he said, “On Thursday the illness of Allah’s Apostle was aggravated and he said, “Fetch me writing materials so that I may have something written to you after which you will never go astray.” The people (present there) differed in this matter and people should not differ before a prophet. They said, “Allah’s Apostle is seriously sick.’ The Prophet said, “Let me alone, as the state in which I am now, is better than what you are calling me for.” The Prophet on his death-bed, gave three orders saying, “Expel the pagans from the Arabian Peninsula,
respect and give gifts to the foreign delegates as you have seen me dealing with them.” I forgot the third (order)” (Ya’qub bin Muhammad said, “I asked Al-Mughira bin ‘Abdur-Rahman about the Arabian Peninsula and he said, ‘It comprises Mecca, Medina, Al-Yama-ma and Yemen.” Ya’qub added, “And Al-Arj, the beginning of Tihama.”)

Sahih Bukhari Book#2 Hadith#24
Ibn ‘Umar(may Allah be pleased with him and his father) who said that the Messenger of Allah (peace be upon him) said:I have been ordered to fight against the people until they testify that none has the right to be worshipped but Allah, to establish the Salah (Prayer) and to perform Zakah (almsgiving), so if they do that, then they save their lives and property from me except legally, and then their reckoning (accounts) will be done by Allah.

Sahih Bukhari Book#8 Hadith#387
Narrated Anas bin Malik: Allah’s Apostle said, “I have been ordered to fight the people till they say: ‘None has the right to be worshipped but Allah.’ And if they say so, pray like our prayers, face our Qibla and slaughter as we slaughter, then their blood and property will be sacred to us and we will not interfere with them except legally and their reckoning will be with Allah.”

Sahih Bukhari Book#52 Hadith#196
Narrated Abu Huraira: Allah ‘s Apostle said, “I have been ordered to fight with the people till they say, ‘None has the right to be worshipped but Allah, and whoever says, ‘None has the right to be worshipped but Allah, his life and property will be saved by me except for Islamic law, and his accounts will be with Allah, (either to punish him or to forgive him.)”

Sahih Muslim Book#1 Hadith#30
It is reported on the authority of Abu Huraira that the Messenger of Allah said: I have been commanded to fight against people so long as they do not declare that there is no god but Allah, and He who professed it was guaranteed the protection of his property and life on my behalf except for the right affairs rest with Allah.

[Narrated by Tirmidhi and Ahmad]
And the Prophet said:
“Do you desire a word which will subdue the Arabs and will cause the non-Arabs to pay the Jizyah to you?” They said: “What is it?” He said: “None has the right to be worshipped except Allah”.

9:29 Fight those who do not believe in Allah or in the Last Day and who do not consider unlawful what Allah and His Messenger have made unlawful and who do not adopt the religion of truth from those who were given the Scripture – [fight] until they give the jizyah willingly while they are humbled.

9:123 O you who have believed, fight those adjacent to you of the disbelievers and let them find in you harshness. And know that Allah is with the righteous.


Sahih Bukhari Book#8 Hadith#387

Narrated Anas bin Malik: Allah’s Apostle said, “I have been ordered to fight the people till they say: ‘None has the right to be worshipped but Allah.’ And if they say so, pray like our prayers, face our Qibla and slaughter as we slaughter, then their blood and property will be sacred to us and we will not interfere with them except legally and their reckoning will be with Allah.”

Hanafi Fiqh
Jihad means to be involved in fighting in the path of Allah by one’s life, wealth, and speech. (al-Badai us-Sanai)
It is further explained to call the unbelievers towards the true Religion of Islam and to fight against them, if they are unwilling to accept this true Religion. (Fathul Qadeer)

Maliki Fiqh
The Muslims are to fight with the Kuffar (disbelievers) to advance Allah’s Religion. (Hashiyatul Adwi/Ash Sharhus Sagir)

Shafi’ee Fiqh
The meaning of Jihad in Shari terms is to make utmost effort in fighting in the path of Allah. (Fathul Bari)

Hanbali Fiqh
Jihad means to fight against the unbelievers. (Matalibe Ulin Nuha)

Imam Al Haleemi in Suab al Iman
Allah clarified that if it weren’t for Allah checking the nonbelievers through the believers and giving the believers authority to protect Islam and break the armies of disbelief, disbelief would have reigned on earth and the true religion would have been eliminated. This proves that the reason for the survival of religion (i.e., Islam) is Jihad and whatever is in this status deserves to be a pillar of Iman.

Imam Shafi’i states
The minimum participation in Jihad is once a year, and more is always better. It is not allowed to have a year pass you by without any fighting except out of necessity like the weakness of Muslims and the great numbers of the enemy, or fear of extermination if you attack them first, or lack of provisions, or similar excuses. Otherwise, if there is no necessity it is not allowed to delay attacking the non-believers for more than a year.

The imam of al Haramain says:
I adopt the opinion of the scholars of usool. They stated that Jihad is a mandatory call and must be established according to the ability until none remains in the world but a Muslim or one who has submitted to Muslims. Thus, Jihad is not limited to once a year. It should be done more frequently if possible. What the scholars of fiqh stated is because usually the time spent in preparations for combat limit the ability to wage war to once a year.

The author of al Mugni from the Hanbali school states
The minimum jihad is once a year
, so it is mandatory every year. If there is a need to fight more than once a year, it becomes mandatory on the Muslims to fulfill that need.

Al Qurtubi states in his tafseer
It is mandatory on the Imam to send an army of Muslims to the land of the enemy once every year and the Imam should participate himself in such expeditions. If not, then he should send someone capable whom he trusts, to call them to Islam, keep away their harm, to give victory to the religion of Allah, until they enter Islam or pay jizyah

Al Inayah Sharh al Hidayah (Hanafi)
Jihad is calling towards the true religion and fighting with one’s soul and wealth against those who reject it.

Mawahib al Jaleel fi Sharh Mukhtasar Khalil (Maliki)
Jihad is a Muslim waging war against a non-Muslim who has no peace agreement with Muslims and the fighting is for the sake of the word of Allah to prevail. Jihad is also fighting the non-Muslim who attacks Muslim territory and it is also the Muslims attacking the non-Muslims in their land.

Book of jihad by Ibn Nuhaas
Jihad is a cure for the individual and the society. It cures the individual by delivering him from the sickness of disbelief to the wellbeing of Islam. Disbelieving in Allah is the greatest disease of all and the most destructive on all humanity, while Islam is the complete cure. Jihad cures the society by eliminating the source of corruption and oppression. Leaving the disbeliever unharmed increases the disease and strengthens it and allows the cancer to spread. Therefore Islam cannot flourish and Muslims cannot live in peace unless the disease is cured.

Alifta
Jihad is not only for defense sake (By Sheikh Ibn Baaz)
http://alifta.net/Fatawa/FatawaChapters.aspx?View=Page&PageID=189&PageNo=1&BookID=14&languagename=

Offensive vs Defensive Jihad by Abdullah Azam
Where the Kuffar are not gathering to fight the Muslims. The fighting becomes fard Kifaya with the minimum requirement of appointing believers to guard borders, and the sending of an army at least once a year to terrorize the enemies of Allah. It is a duty Of upon the Imam to assemble and send out an army unit into the land of war once or twice every year. Moreover, it is the responsibility of the Muslim population to assist him, and if he does not send an army he is in sin. And the Ulama have mentioned that this type of jihad is for maintaining the payment of Jizya. The scholars of the principles of religion have also said: “Jihad is Da’wah with a force, and is obligatory to perform with all available capabilities, until there remains only Muslims or people who submit to Islam.”
http://www.systemoflife.com/articles/general/170-offensive-jihad-vs-defensive-jihad#axzz3VOTsOY61

Definition and ruling of Jihad by Muhammad Masood Azhar
Offensive Jihad is when the Muslims launch an offensive attack. If this attack is on the Kuffar who have previously received the message of Islam, then to call them towards Islam before commencement of the attack is considered preferable. If the message of Islam has not reached them, then the kuffar will be invited towards Islam. If threy reject this true faith, then they will have to pay Jizyah (Kufr Tax). If they refuse to submit to the payment of Jizyah then the Muslims are to fight against them.
It is stated in Fatawa Shami: “It is required of the Imam (leader) of the Muslims to dispatch the army routinely once or twice a year towards the kufr countries. It is also the duty of the Muslim public to assist the Imam in this noble cause. If the Imam does not send an army, then he will be considered sinful.”
The majority of Jihad undertaken at the time of our Prophet Muhammad (salallahu ‘alayhi wasallam) was within the category of offensive Jihad. ”
http://www.muftisays.com/blog/Seifeddine-M/1154_08-02-2011/definition-and-ruling-of-jihad.html

Muslims are very quick to point out the concept of Mahr(Dowry) when they talk about Women rights. If you read from Quran and Hadiths, this money / gift is basically given by husband to have SEXUAL INTERCOURSE with his wife.

4:24 (Also prohibited are) the women already bound in marriage, except the bondwomen you come to own. It has been written by Allah for you. All (women), except these, have been permitted for you to seek (to marry) through your wealth, binding yourself, (in marriage) and not only for lust. So, to those of them whose company you have enjoyed, give their dues (dower) as obligated. There is no sin on you in what you mutually agree upon after the (initial) agreement. Surely, Allah is All-Knowing, All-Wise. [Translation of Mufti Taqi Usmani]

If you read the verse above it clearly states whose company you have enjoyed, give their dues as obligated. Isn’t it similar to what a man will give to a prostitute after enjoying her company ?

Tafsir Ibn Kathir
(provided you seek them (with a dowry) from your property, desiring chastity, not fornication,) meaning, you are allowed to use your money to marry up to four wives and for (the purchase of) as many female slaves as you like, all through legal means,((desiring) chastity, not fornication.) Allah’s statement,

(So with those among them whom you have enjoyed, give them their required due,) means, to enjoy them sexually, surrender to them their rightful dowry as compensation. In other Ayat, Allah said,
(And how could you take it (back) while you have gone in unto each other),

Maariful Quran
(So, whoever of them you have benefited from, give them their due as obligated): ‘Benefiting’ in this verse refers to coition and it means that the payment of full dower is due on the husband only when he had benefited from her company by having sex with her
. If, after the initial marriage contract the wife has not come to live with the husband who thus does not get the opportunity to ‘benefit’ from her company, and he divorces her before having that opportunity, the payment of mahr (dower) due against him becomes half. Special attention has been drawn in this verse to the situation when, once this ‘benefit’ has been received from some woman, the payment of her mahr becomes obligatory on all counts.

Tafsir Al-Jalalayn
And, forbidden to you are, wedded women, those with spouses, that you should marry them before they have left their spouses, be they Muslim free women or not; save what your right hands own, of captured [slave] girls, whom you may have sexual intercourse with, even if they should have spouses among the enemy camp, but only after they have been absolved of the possibility of pregnancy [after the completion of one menstrual cycle]; this is what God has prescribed for you (kitāba is in the accusative because it is the verbal noun). Lawful for you (read passive wa-uhilla, or active wa-ahalla), beyond all that, that is, except what He has forbidden you of women, is that you seek, women, using your wealth, by way of a dowry or a price, in wedlock and not, fornicating, in illicitly. Such wives as you enjoy thereby, and have had sexual intercourse with, give them their wages, the dowries that you have assigned them, as an obligation; you are not at fault in agreeing together, you and they, after the obligation, is waived, decreased or increased. God is ever Knowing, of His creatures, Wise, in what He has ordained for them.

Tafsir Ibn Abbas
(And all married women (are forbidden unto you save those (captives) whom your right hands possess) of captives, even if they have husbands in the Abode of War, after ascertaining that they are not pregnant, by waiting for the lapse of one period of menstruation. (It is a decree of Allah for you) that which I have mentioned to you is unlawful in Allah’s Book. (Lawful unto you are all beyond those mentioned) as unlawful, (so that ye seek them) marry (with your wealth) up to four wives; it is also said that this means: so that you buy with your wealth captives; and it is also said that this means: so that you should seek with your money marrying women for an agreed period of time (zawaj al-mut’ah) but the lawfulness of this practice was later abrogated, (in honest wedlock) He says: be with them as legitimate husbands, (not debauchery) not indulging in adultery without having a proper marriage. (And those of whom) after marriage (ye seek content) from whom you derive benefit, (give unto them their portions) give to them their full dowry (as a duty) as an obligation upon you from Allah to give the dowry in full. (And there is no sin for you) there is no harm for you (in what ye do by mutual agreement) in increasing or decreasing the amount of the dowry by mutual agreement (after the duty hath been done) after the first obligation to which you have aspired. (Lo! Allah is ever Knower) in relation to making lawful to you marriage for an agreed, limited period of time, (Wise) in later making this practice unlawful; it is also said that this means: Allah is ever Knower of your compulsion for marriage for an agreed, limited period of time, Wise in making such marriage unlawful.

Al Quraishi Tafsir
And wedded women, save what your right hands own, this is what God has prescribed for you. Lawful for you beyond all that is that you seek using your wealth, in wedlock and not in illicitly. Such wives as you enjoy thereby, give them their wages as an obligation; you are not at fault in agreeing together, after the obligation. God is ever Knowing,Wise.
When you stay mindful of the limits, respect agreements and obtain mutual consent with women according to the law, there will be no enmity in it for people and no punishment to follow from it from the Real (s), for that is lawful and without further restriction.

Sahih Bukhari Volume 7, Book 63, Number 262
Narrated Ibn ‘Umar:
The Prophet said to those who were involved in a case of Lian, “Your accounts are with Allah. One of you two is a liar. You (husband) have right on her (wife).” The husband said, “My money, O Allah’s Apostle!” The Prophet said, “You are not entitled to take back any money. If you have told the truth, the mahr that you paid, was for having sexual relations with her lawfully; and if you are a liar, then you are less entitled to get it back.”

Sahih Bukhari Volume 7, Book 63, Number 261
Narrated Said bin Jubair:
I said to Ibn ‘Umar, “If a man accuses his wife of illegal sexual intercourse (what is the judgment)?” He said, “Allah’s Prophet separated the couple of Bani ‘Ajlan (when the husband accused his wife for an illegal sexual intercourse). The Prophet said, ‘Allah knows that one of you two IS a liar; so will one of you repent?’ But they refused. He then again said, ‘Allah knows that one of you two is a liar; so will one of you repent?’ But they refused, whereupon he separated them by divorce.” Aiyub (a sub-narrator) said: ‘Amr bin Dinar said to me, “In the narration there is something which I do not see you mentioning, i.e. the husband said, “What about my money (Mahr)?‘ The Prophet said, “You are not entitled to take back money, for if you told the truth you have already entered upon her and if you are a liar then you are less entitled to take it back.

Sunan Abu Dawood , Kitab Al-Nikah #2078
Narrated Aisha, Ummul Mu’minin: The Apostle of Allah (peace_be_upon_him) said: The marriage of a woman who marries without the consent of her guardians is void. (He said these words) three times. If there is cohabitation, she gets her dower for the intercourse her husband has had . If there is a dispute, the sultan (man in authority) is the guardian of one who has none.

Sunan Abu Dawood , Kitab Al-Nikah #2121
Narrated A man from the Companion of the Prophet: Muhammad ibn AbdurRahman ibn Thawban reported on the authority of a man from the Companions of the Prophet (peace_be_upon_him): When Ali married Fatimah, daughter of the Apostle of Allah (peace_be_upon_him), he intended to have intercourse with her. The Apostle of Allah (peace_be_upon_him) prohibited him to do so until he gave her something. Ali said: I have nothing with me, Apostle of Allah. The Prophet (peace_be_upon_him) said: Give her your coat of mail. So he gave her his coat of mail, and then cohabited with her.

Sunan Abu Dawood , Kitab Al-Nikah #2126
Narrated Basrah: A man from the Ansar called Basrah said: I married a virgin woman in her veil. When I entered upon her, I found her pregnant. (I mentioned this to the Prophet). The Prophet (peace_be_upon_him) said: she will get the dower, for you made her vagina lawful for you. The child will be your slave. When she has begotten (a child), flog her (according to the version of al-Hasan). The version of Ibn AbusSari has: You people, flog her, or said: inflict hard punishment on him.

Sunan Abu Dawood , Kitab Al-Talaq #2228
Narrated Aisha, Ummul Mu’minin: Barirah was emancipated, and she was the wife of Mughith, a slave of Aal AbuAhmad. The Apostle of Allah (peace_be_upon_him) gave her choice, and said to her: if he has intercourse with you , then there is no choice for you.

Al-Muwatta’, 2/734
In our view the man who rapes a woman, whether she is a virgin or not, if she is a free woman he must pay a dowry like that of her peers, and if she is a slave he must pay whatever has been detracted from her value. The punishment is to be carried out on the rapist and there is no punishment for the woman who has been raped, whatever the case.

4:24 And [also prohibited to you are all] married women except those your right hands possess. [This is] the decree of Allah upon you. And lawful to you are [all others] beyond these, [provided] that you seek them [in marriage] with [gifts from] your property, desiring chastity, not unlawful sexual intercourse. So for whatever you enjoy [of marriage] from them, give them their due compensation as an obligation. And there is no blame upon you for what you mutually agree to beyond the obligation. Indeed, Allah is ever Knowing and Wise.

Tafsir Ibn Kathir
Allah said,
(Also (forbidden are) women already married, except those whom your right hands possess.) The Ayah means, you are prohibited from marrying women who are already married,
(except those whom your right hands possess) except those whom you acquire through war, for you are allowed such women after making sure they are not pregnant. Imam Ahmad recorded that Abu Sa`id Al-Khudri said, “We captured some women from the area of Awtas who were already married, and we disliked having sexual relations with them because they already had husbands. So, we asked the Prophet about this matter, and this Ayah was revealed,
(Also (forbidden are) women already married, except those whom your right hands possess). Consequently, we had sexual relations with these women.” This is the wording collected by At-Tirmidhi An-Nasa’i, Ibn Jarir and Muslim in his Sahih. Allah’s statement,
(Thus has Allah ordained for you) means, this prohibition was ordained for you by Allah. Therefore, adhere to Allah’s Book, do not transgress His set limits, and adhere to His legislation and decrees.

Tafsir Ibn Abbas
(And all married women (are forbidden unto you save those (captives) whom your right hands possess) of captives, even if they have husbands in the Abode of War, after ascertaining that they are not pregnant, by waiting for the lapse of one period of menstruation. (It is a decree of Allah for you) that which I have mentioned to you is unlawful in Allah’s Book. (Lawful unto you are all beyond those mentioned) as unlawful, (so that ye seek them) marry (with your wealth) up to four wives; it is also said that this means: so that you buy with your wealth captives; and it is also said that this means: so that you should seek with your money marrying women for an agreed period of time (zawaj al-mut’ah) but the lawfulness of this practice was later abrogated, (in honest wedlock) He says: be with them as legitimate husbands, (not debauchery) not indulging in adultery without having a proper marriage. (And those of whom) after marriage (ye seek content) from whom you derive benefit, (give unto them their portions) give to them their full dowry (as a duty) as an obligation upon you from Allah to give the dowry in full. (And there is no sin for you) there is no harm for you (in what ye do by mutual agreement) in increasing or decreasing the amount of the dowry by mutual agreement (after the duty hath been done) after the first obligation to which you have aspired. (Lo! Allah is ever Knower) in relation to making lawful to you marriage for an agreed, limited period of time, (Wise) in later making this practice unlawful; it is also said that this means: Allah is ever Knower of your compulsion for marriage for an agreed, limited period of time, Wise in making such marriage unlawful.

Sahih Muslim Book#008 Hadith#3432
Abu Sa’id al-Khudri reported that at the Battle of Hunain Allah’s Messenger sent an army to Autas and encountered the enemy and fought with them. Having overcome them and taken them captives, the Companions of Allah’s Messenger seemed to refrain from having intercourse with captive women because of their husbands being polytheists. Then Allah, Most High, sent down regarding that:” And women already married, except those whom your right hands possess (Quran 4:. 24)” (i. e. they were lawful for them when their ‘Idda period came to an end).

Sahih Muslim Book#008 Hadith#3433
Abu Sa’id al-Khudri (Allah be pleased with him) reported that Allah’s Apostle (may peace be upon him) sent a small army. The rest of the hadith is the same except this that he said: Except what your right hands possessout of them are lawful for you; and he did not mention” when their ‘idda period comes to an end”. This hadith has been reported on the authority of AbuSa’id (al-Khudri) (Allah be pleased with him) through another chain of transmitters and the words are: They took captives (women) on the day of Autas who had their husbands. They were afraid (to have sexual intercourse with them) when this verse was revealed:” And women already married except those whom you right hands posses” (iv. 24) 

Abu Dawud 2:2150
Abu Said al-Khudri said: “The apostle of Allah sent a military expedition to Awtas on the occasion of the battle of Hunain. They met their enemy and fought with them. They defeated them and took them captives. Some of the Companions of the apostle of Allah were reluctant to have intercourse with the female captives in the presence of their husbands who were unbelievers. So Allah, the Exalted, sent down the Quranic verse, “And all married women (are forbidden) unto you save those (captives) whom your right hands possess”. That is to say, they are lawful for them when they complete their waiting period.”

65:4 And those who no longer expect menstruation among your women – if you doubt, then their period is three months, and [also for] those who have not menstruated. And for those who are pregnant, their term is until they give birth. And whoever fears Allah – He will make for him of his matter ease.

Tafsir Ibn Abbas
(And for such of your women as despair of menstruation) because of old age, (if ye doubt) about their waiting period, (their period (of waiting) shall be three months) upon which another man asked: “O Messenger of Allah! What about the waiting period of those who do not have menstruation because they are too young?” (along with those who have it not) because of young age, their waiting period is three months. Another man asked: “what is the waiting period for those women who are pregnant?” (And for those with child) i.e. those who are pregnant, (their period) their waiting period (shall be till they bring forth their burden) their child. (And whosoever keepeth his duty to Allah) and whoever fears Allah regarding what he commands him, (He maketh his course easy for him) He makes his matter easy; and it is also said this means: He will help him to worship Him well.

Tafsir Ibn Kathir
Allah the Exalted clarifies the waiting period of the woman in menopause. And that is the one whose menstruation has stopped due to her older age. Her `Iddah is three months instead of the three monthly cycles for those who menstruate, which is based upon the Ayah in (Surat) Al-Baqarah. ?see 2:228? The same for the young, who have not reached the years of menstruation. Their `Iddah is three months like those in menopause. This is the meaning of His saying;
(and for those who have no courses…) as for His saying;
(if you have doubt…) There are two opinions: First, is the saying of a group of the Salaf, like Mujahid, Az-Zuhri and Ibn Zayd. That is, if they see blood and there is doubt if it was menstrual blood or not. The second, is that if you do not know the ruling in this case, then know that their `Iddah is three months. This has been reported from Sa`id bin Jubayr and it is the view preferred by Ibn Jarir. And this is the more obvious meaning. Supporting this view is what is reported from Ubay bin Ka`b that he said, “O Allah’s Messenger! Some women were not mentioned in the Qur’an, the young, the old and the pregnant.” Allah the Exalted and Most Honored sent down this Ayah,
(Those in menopause among your women, for them the `Iddah, if you have doubt, is three months; and for those who have no courses. And for those who are pregnant, their `Iddah is until they lay down their burden.) Ibn Abi Hatim recorded a simpler narration than this one from Ubay bin Ka`b who said, “O Allah’s Messenger! When the Ayah in Surat Al-Baqarah was revealed prescribing the `Iddah of divorce, some people in Al-Madinah said, `There are still some women whose `Iddah has not been mentioned in the Qur’an. There are the young, the old whose menstruation is discontinued, and the pregnant.’ Later on, this Ayah was revealed,
(Those in menopause among your women, for them the `Iddah, if you have doubt, is three months; and for those who have no courses.)”

Tafsir Al-Jalalayn
And [as for] those of your women who (read alla’i or alla’i in both instances) no longer expect to menstruate, if you have any doubts, about their waiting period, their prescribed [waiting] period shall be three months, and [also for] those who have not yet menstruated, because of their young age, their period shall [also] be three months — both cases apply to other than those whose spouses have died; for these [latter] their period is prescribed in the verse: they shall wait by themselves for four months and ten [days] [Q. 2:234]. And those who are pregnant, their term, the conclusion of their prescribed [waiting] period if divorced or if their spouses be dead, shall be when they deliver. And whoever fears God, He will make matters ease for him, in this world and in the Hereafter.

Maududi
They may not have menstruated as yet either because of young age, or delayed menstrual discharge as it happens in the case of some women, or because of no discharge at all throughout life which, though rare, may also be the case. In any case, the waiting-period of such a woman is the same as of the woman, who has stopped menstruation. That is three months from the time divorce was pronounced.
Here, one should bear in mind the fact that according to the explanations given in the Quran the question of the waiting period arises in respect of the women with whom marriage may have been consummated, for there is no waiting period in case divorce is pronounced before the consummation of marriage. (Surah Al-Ahzab, Ayat 49). Therefore, making mention of the waiting-period for the girls who have not yet menstruated, clearly proves that it is not only permissible to give away the girl in marriage at this age but it is also permissible for the husband to consummate marriage with her. Now, obviously no Muslim has the right to forbid a thing which the Quran has held as permissible. The girl who is divorced in the state when she has not yet menstruated and then she starts having the menses during the waiting-period, will reckon her waiting-period from the same menstruation and her waiting-period will be reckoned just like the woman who menstruates regularly.

Maariful Quran
This verse deals with additional rules pertaining to the waiting-period of divorced women. It subdivides divorced women and their waiting-periods into three different categories. Under normal circumstances, the waiting-period of a divorced woman is three menstrual cycles as mentioned in Sirah Al-Baqarah. In the case of women who have stopped menstruating for good on account of advanced age, or due  to some disease etc. their “iddah is three months instead of three cycles. The same is the “iddah of young women who have not yet started menstruating on account of being under age. The iddah for women who are pregnant at the time of divorce continues until they give birth to their child irrespective of the length of the period.

Islam QA

“Marriage to a young girl before she reaches puberty is permissible according to sharee’ah, and it was narrated that there was scholarly consensus on this point. ”
http://islamqa.com/en/ref/12708/

Islamweb

So, Allah set rulings of marriage, divorce and waiting period for the women who have not yet had menses, i.e. the young girls.The Iddah (waiting period) does not take place except after marriage.

Ibn Qudama said in Al-Mughni There is no difference as regards a young girl who is still a virgin”. Ibn Al-Mundhir said: “The reliable people of knowledge agree unanimously that it is permissible for a father to marry off his young and virgin daughter to an eligible man. It is also permissible for him to marry her off despite her reluctance to be married.”

Al Baghawi said, like in Fath Al-Bari, “There is a consensus of the scholars that it is permissible for the fathers to marry their young daughters even if they are still in the cradle, but it is not permissible for the husbands to consummate the marriage with them, unless they become physically fit for sexual intercourse by mature males.”
http://www.islamweb.net/emainpage/index.php?page=showfatwa&Option=FatwaId&Id=88089

Alifta

Marriage is not limited to a certain minimum or maximum age by the Qur’an or the Sunnah (whatever is reported from the Prophet).They both encourage Marriage and awaken a desire for it without specifying a certain age
4:127 They ask your legal instruction concerning women, say: Allâh instructs you about them, and about what is recited unto you in the Book concerning the orphan girls whom you give not the prescribed portions (as regards Mahr and inheritance) and yet whom you desire to marry.
It gives permission to marry an orphan girl, defined as the one who has not attained the age of puberty yet, which is maximally at the age of fifteen, as is most likely, yet she may attain it at a lesser age.”
http://alifta.net/Fatawa/FatawaChapters.aspx?View=Page&PageID=285&PageNo=1&BookID=14

Baheshti Zewar

12. If a boy or a girl are immature, they do not have their own choice. Their nikâh is not valid without a wali. If a boy (or girl) performs his nikâh on his own or someone else performs it, it will be dependent on the permission of the wali. If the wali grants permission, the nikâh will be valid. If not, it will not be valid. The wali has full rights over such a boy or girl. He can get them married to whoever he wishes and refuse whoever he wishes. Immature girls and immature boys cannot reject such a nikâh at that time. This is irrespective of whether the girl is a virgin or had been married previously and had also been sent to her (first) husband’s home – the same rule will apply.
http://www.islamicbulletin.org/free_downloads/women/bahishti_4_5_6_7.pdf

Tafheem

And if the woman is such a one marriage with whom has been consummated who no longer menstruates, or the one who has not yet menstruated, she can be divorced even after the sexual intercourse for there is no chance of her being pregnant.

13. They may not have menstruated as yet either because of young age, or delayed menstrual discharge as it happens in the case of some women, or because of no discharge at all throughout life which, though rare, may also be the case. In any case, the waiting-period of such a woman is the same as of the woman, who has stopped menstruation. That is three months from the time divorce was pronounced.

Here, one should bear in mind the fact that according to the explanations given in the Quran the question of the waiting period arises in respect of the women with whom marriage may have been consummated, for there is no waiting period in case divorce is pronounced before the consummation of marriage. (Surah Al-Ahzab, Ayat 49). Therefore, making mention of the waiting-period for the girls who have not yet menstruated, clearly proves that it is not only permissible to give away the girl in marriage at this age but it is also permissible for the husband to consummate marriage with her. Now, obviously no Muslim has the right to forbid a thing which the Quran has held as permissible.
http://www.islamicstudies.info/tafheem.php?sura=65&verse=1&to=7

Darul Uloom Deoband

15. A wali other than the father or grand-father had performed the nikah of an immature girl who also had knowledge of this nikah. Thereafter, she became mature and until then her husband hadn’t had any sexual intercourse with her. In such a case, the moment she becomes mature, she must mention her discontent with regard to marrying this person. She must clearly state that she is not happy. Alternatively, she could say that she does not wish to continue with this marriage. This could be said in the presence of others or in privacy where she is all alone. But she has to mention it verbally. However, by her merely saying this, the nikah will not be annulled. She will have to go to a Muslim judge, he will annul the marriage, and only then will it be annulled.

Once she becomes mature and allows even a moment to pass in which she does not mention her discontent, she will not have the choice of having her nikah annulled.

But if the girl did not have any knowledge of this nikah and only learnt of it after becoming mature, then the moment she is informed, she will immediately have the right to reject the nikah. If she remains silent for even a moment, she will forfeit this right to reject the nikah.

16. If her husband engaged in sexual intercourse with her, and thereafter she becomes mature, it is not necessary for her to reject the nikah immediately after becoming mature or after being informed. Instead, as long as she does not express her consent and happiness, she will have the choice of rejecting or accepting irrespective of how much time lapses. However, if she clearly states that she is happy about this marriage, or her consent is made apparent in some other way such as being in solitude with her husband like any other normal husband and wife, then she will have no choice and this nikah will become entrenched.
http://www.darululoom-deoband.com/english/books/nikah.htm