[4:92] No believer shall kill another believer, unless it is an accident. If one kills a believer by accident, he shall atone by freeing a believing slave, and paying a compensation to the victim's family, unless they forfeit such a compensation as a charity. If the victim belonged to people who are at war with you, though he was a believer, you shall atone by freeing a believing slave. If he belonged to people with whom you have signed a peace treaty, you shall pay the compensation in addition to freeing a believing slave. If you cannot find a slave to free, you shall atone by fasting two consecutive months, in order to be redeemed by GOD. GOD is Knower, Most Wise.
(5:89) Allah does not take you to task for the oaths you utter vainly, but He will certainly take you to task for the oaths you have sworn in earnest. The expiation (for breaking such oaths) is either to feed ten needy persons with more or less the same food as you are wont to give to your families, or to clothe them, or to set free from bondage the neck of one man; and he who does not find the means shall fast for three days. This shall be the expiation for your oaths whenever you have sworn (and broken them.) But do keep your oaths. Thus does Allah make clear to you His commandments; maybe you will be grateful.
(58:3) Those who declare their wives to be their mothers and thereafter go back on what they have said shall free a slave before they may touch each other. That is what you are exhorted to do. Allah is fully aware of all your deeds.
(90:13) It is freeing someone's neck from slavery
(24:33) Let those who cannot afford to marry keep themselves chaste until Allah enriches them out of His Bounty. And write out a deed of manumission for such of your slaves that desire their freedom in lieu of payment - if you see any good in them - and give them out of the wealth that Allah has given you. And do not compel your slave-girls to prostitution for the sake of the benefits of worldly life the while they desire to remain chaste. And if anyone compels them to prostitution, Allah will be Most Pardoning, Much Merciful (to them) after their subjection to such compulsion.
[9:60] The alms are meant only for the poor and the needy and those who are in charge thereof, those whose hearts are to be reconciled, and to free those in bondage, and to help those burdened with debt, and for expenditure in the Way of Allah and for the wayfarer. This is an obligation from Allah. Allah is All-Knowing, All-Wise.
(2:177) Righteousness does not consist in turning your faces towards the east or towards the west; true righteousness consists in believing in Allah and the Last Day, the angels, the Book and the Prophets, and in giving away one’s property in love of Him to one’s kinsmen, the orphans, the poor and the wayfarer, and to those who ask for help, and in freeing the necks of slaves, and in establishing Prayer and dispensing the Zakah. True righteousness is attained by those who are faithful to their promise once they have made it and by those who remain steadfast in adversity and affliction and at the time of battle (between Truth and falsehood). Such are the truthful ones; such are the God-fearing.
(2:221) Marry not the women who associate others with Allah in His Divinity until they believe; for a believing slave-girl is better than a (free, respectable) woman who associates others with Allah in His Divinity, even though she might please you. Likewise, do not give your women in marriage to men who associate others with Allah in His Divinity until they believe; for a believing slave is better than a (free, respectable) man who associates others with Allah in His Divinity, even though he might please you. Such people call you towards the Fire,237 and Allah calls you, by His leave, towards Paradise and forgiveness; and He makes His injunctions clear to people so that they may take heed.
(4:25) And those of you who cannot afford to marry free, believing women (muhsanat), then marry such believing women whom your right hands possess. Allah knows all about your faith. All of you belong to one another. Marry them, then, with the leave of their guardians, and give them their bridal-due in a fair manner that they may live in the protection of wedlock rather than be either mere objects of unfettered lust or given to secret love affairs. Then if they become guilty of immoral conduct after they have entered into wedlock, they shall be liable to half the penalty to which free women (muhsanat) are liable. This relaxation is for those of you who fear to fall into sin by remaining unmarried. But if you persevere, it is better for you. Allah is All-Forgiving, All-Compassionate.
(4:36) Serve Allah and ascribe no partner to Him. Do good to your parents, to near of kin, to orphans, and to the needy, and to the neighbor who is of kin and to the neighbor who is a stranger, and to the companion by your side, and to the wayfarer, and to those whom your right hands possess. Allah does not love the arrogant and the boastful.
Below are relevant Traditions (ahadith) encouraging emancipation of slaves, Muslims and non-Muslims alike:
“Give food to the hungry, pay a visit to the sick and release (set free) the one in captivity (by paying his ransom).” - Muhammad (S) [Bukhari: Abu Musa Al-Ash’ari (RA)]
“Allah the Most High said, I will be the opponent of three persons on the Day of Resurrection. They are the one who makes a covenant in My name and then prove treacherous. Or the one who sells a free person (Muslim or non-Muslim) as a slave and appropriates his price for himself. And the one who hires a laborer and having taken full work from him, fails to pay him his wages.” - Muhammad (S) [Hadith Qudsi, Bukhari: Abu Hurayrah (RA)]
“There are three people whose prayers are not accepted. And one of these three is a man who enslaves a free person (Rajulun iitabada muharraran).” – Muhammad (S) [Abu Dawud
Muhammad Asad, respected author and one of the leading translators and commenters on the Qur’an explains (Note 146 Qur’an Ref: 2:177)
“Ar-raqabah (of which ar-riqab is the plural) denotes, literally, "the neck", and signifies also the whole of a human person. Metonymically, the expression fi 'r-riqab denotes "in the cause of freeing human beings from bondage", and applies to both the ransoming of captives and the freeing of slaves. By including this kind of expenditure within the essential acts of piety, the Qur'an implies that the freeing of people from bondage - and, thus, the abolition of slavery - is one of the social objectives of Islam...the Qur'an stresses the great merit inherent in the freeing of slaves, and stipulates it as a means of atonement for various transgressions (see, e.g., 4:92, 5:89, 58:3). In addition, the Prophet emphatically stated on many occasions that, in the sight of God, the unconditional freeing of a human being from bondage is among the most praiseworthy acts which a Muslim could perform. (For a critical discussion and analysis of all the authentic Traditions bearing on this problem, see Nayl al-Awtar VI, 199 ff.)
Many of the earliest followers of Islam were slaves and former slaves. Slavery disappeared in much of the Islamic world, in accordance with the Qur’an’s teaching on equality and freedom. Throughout the centuries, Muslim advocates spoke out against slavery around the world.