Slavery is a concept that existed since pre-recorded history. However the way it was practiced in the Islamic world differs greatly than how it was practiced in the rest of the world. Even in the more recent times, centuries after the introduction of Islam, the non-Muslims have practiced slavery in the most barbaric manner.
The whole Trans-Atlantic nonsense that was practiced by the Americans is one of the worst forms of slavery man has witnessed. The slaves were not treated as humans and did not have any rights. This way was much similar to the form practiced before the advent of Islam in the Times of Ignorance (Ja'hilah).
Islam indeed came as a blessing to all Mankind and it was seen that slaves were given rights, something which the rest of the world never gave them. Slowly paving the way of totally uprooting the slavery system by establishing their distinctive identity, their rights and then setting them free and bold instructions of setting them free and looking to protect their rights.
Treatment of Slaves
Apart from giving the slaves their rights, Islam also took it a step ahead and discouraged slavery from being practiced. It is seen in history that slaves were mistreated to a great extent in the non-Islamic world. Not only were they verbally abused, they were physically abused as well. The master would overburden the slave and make them work all day. Slaves would wear torn and tattered clothes while the masters would dress with the finest threads available.
When it would come to food, the slaves would get leftovers or if not, very little food which would certainly not include good quality food. Some would not even get meat or fruits which their masters ate. Prophet Muhammad (saw) with Divine Inspiration from Allah (swt) forbade such acts. Masters could not abuse their slaves and had to give them the same that they ate and wore.
Narated by Al-Ma'rur: At Ar-Rabadha I met Abu Dhar who was wearing a cloak, and his slave, too, was wearing a similar one. I asked about the reason for it.
He replied, "I abused a person by calling his mother with bad names." The Prophet said to me, 'O Abu Dhar! Did you abuse him by calling his mother with bad names, you still have some characteristics of ignorance. Your slaves are your brothers and Allah has put them under your command. So whoever has a brother under his command should feed him of what he eats and dress him of what he wears. Do not ask them (slaves) to do things beyond their capacity (power) and if you do so, then help them.' " – [Bukhari, Vol.1, Book 2, #29]
The introduction of Islam and with the application of Islam by Muslims, slavery had a new meaning altogether. It no longer meant that you have a beast under your control and hence you could abuse it, make it work like a donkey all day and at the end of the day give it crumbs to eat so that it stays alive.
Islam made it clear to every follower that a human being who is a slave is yet the brother of a Muslim and the slave had their rights which is compulsory for a Muslim to fulfill. It taught that slaves and masters are equal in the sights of Allah (swt) and if a Muslim was given a brother under his command then he had to make sure that the brother was given the rights which Islam prescribed.
In another narration the importance of giving slaves education and teaching them good manners is stressed by Prophet Muhammad (saw):
Narrated Abu Burda's father: Allah's Apostle said "Three persons will have a double reward:
1. A Person from the people of the scriptures who believed in his prophet (Jesus or Moses) and then believed in the Prophet Muhammad (i .e. has embraced Islam).
2. A slave who discharges his duties to Allah and his master.
3. A master of a woman-slave who teaches her good manners and educates her in the best possible way (the religion) and manumits her and then marries her." – [Bukhari Vol.1, Book 3, #97A]
Here it is seen that not only education has been given importance but slavery is also discouraged. It is well known that a person belonging to the People of the Book would receive a double reward for accepting Islam. Similarly the same double reward is offered to a person who would free his woman-slave and marry her after giving her education and teaching her good manners. This way slavery is discouraged in the Islamic world.
The Muslims were also forbidden from forcing their slave-girls into prostitution so that they would earn money out of it. There was an incident when the slave-girl of an Ansari was forced after which a verse relating to the act was revealed by Allah (swt).
Narated by Jabir ibn Abdullah: Musaykah, a slave-girl of some Ansari, came and said: My master forces me to commit fornication. Thereupon the following verse was revealed: "But force not your maids to prostitution (when they desire chastity)." – [Abu Dawud, Book 6, #2304]
The Lessons of Equality
There can be found numerous evidences in the Islamic traditions which teach us that slaves are to be treated like any other human being. People belonging to the days of ignorance would not even stand next to a slave while Muslims stand next to them in prayers showing a sign of unity and uniformity in their status in front of Allah (swt).
Hazrat Bilal was one of the first slaves to accept Islam. He was tortured by the pagans so that he would renounce Islam and come back to the pagan ways. However he did not reject Islam and adhered to the teachings of Prophet Muhammad (saw). He was also the first person to stand on top of the Ka'aba and give the Adhan (the Muslim call for prayer).
It is also important to note that further evidence for the equality and recognition of slaves as normal human beings is seen in the numerous ahadith narrated by the slaves and freed slaves that are considered as true and followed by millions of Muslims in the world today. This means that their testimony is also recognized and accepted. We can also see from the traditions that slaves would not only stand shoulder to shoulder with others Muslims during prayer but would also lead the prayers.
Narrated Ibn 'Umar: When the earliest emigrants came to Al-'Usba a place in Quba', before the arrival of the Prophet- Salim, the slave of Abu Hudhaifa, who knew the Qur'an more than the others used to lead them in prayer. – [Bukhari, Vol.1, Book 11, #661]
In the Quran one can see clearly that the woman-slaves and man-slaves who have accepted Islam are better than the free women and men from the disbelievers. Muslims are advised to get the son or daughter married to a woman-slave or man-slave rather than a free, vile, unchaste woman or man from among the idolaters.
Do not marry unbelieving women (idolaters), until they believe: A slave woman who believes is better than an unbelieving woman, even though she allures you. Nor marry (your girls) to unbelievers until they believe: A man slave who believes is better than an unbeliever, even though he allures you. Unbelievers do (but) beckon you to the Fire. But Allah beckons by His Grace to the Garden (of bliss) and forgiveness, and makes His Signs clear to mankind: That they may celebrate His praise. – [Quran 2:221]
Islam goes a step ahead in giving respect to the slaves and it is narrated that Prophet Muhammad(saw) asked people not to refer to a slave saying "this is my slave" but rather to say "this is my man" or "this is my woman".
Islam Stresses on Freeing Slaves
Importance was stressed upon manumitting(freeing of slaves) slaves a lot by Allah (swt) through his last and final Prophet (saw). Even if a disbeliever practiced slave-manumitting before accepting Islam, it is told that he would yet be rewarded for this good deed after accepting Islam. In Islam there is a concept that all good done for the sake of Allah (swt) will be rewarded and all those done for other causes e.g. fame, fortune etc will not be rewarded in the Hereafter. Manumitting slaves is among those good deeds which are rewarded even if done before accepting Islam.
Narrated Hakim bin Hizam: I said to Allah's Apostle, "Before embracing Islam I used to do good deeds like giving in charity, slave-manumitting, and the keeping of good relations with Kith and kin. Shall I be rewarded for those deeds?" The Prophet replied, "You became Muslim with all those good deeds (Without losing their reward)." – [Bukhari, Vol.2, Book 24, #517]