Dear brother,
I send you some explanations from Wisdom Fund. Read them carefully, please.
http://www.twf.org/Library/Slavery.html
Slavery in Islam
The Quran
O mankind! We created you from a single soul, male and female, and made you into nations and tribes, so that you may come to know one another. Truly, the most honored of you in God's sight is the greatest of you in piety. God is All-Knowing, All-Aware. -- 49:13
Prophet Muhammad, 570--632 AD
. . . yield obedience to my successor, although he may be an Abyssinian slave.
He will not enter paradise who behaveth ill to his slaves. The companions said, "O Apostle of God! Have you not told us, that there will be a great many slaves and orphans amongst your disciples?" He said, "Yes; then be kind to them as your own children, and give them to eat of what you eat yourselves. The slaves that say their prayers are your brothers."
[The first call to prayer at the Quba mosque built by Prophet Muhammad was given in 622 by Bilal -- a black slave freed by the Prophet. The Supreme Court of the United States declared in 1857 that the slave Dred Scott could not sue for his freedom because he was not a person, but property.]
Annemarie Schimmel, Islam: An Introduction
Slavery was not abolished by the Koran, but believers are constantly admonished to treat their slaves well. In case of illness a slave has to be looked after and well cared for. To manumit [free] a slave is higly meritorious; the slave can ransom himself by paying some of the money he has earned while conducting his own business. Only children of slaves or non-Muslim prisoners of war can become slaves, never a freeborn Muslim; therefore slavery is theoretically doomed to disappear with the expansion of Islam. The entire history of Islam proves that slaves could occupy any office, and many former military slaves, usually recruited from among the Central Asian Turks, became military leaders and often even rulers as in eastern Iran, India (the Slave Dynasty of Delhi), and medieval Egypt (the Mamluks). Eunuchs too served in important capacities, not only as the guardians of the women's quarters, but also in high administrative and military positions. -- p. 67
Roger Du Pasquier, Unveiling Islam
To answer this question, it should first be remarked that Islam has tolerated slavery but has never approved of it, and that all its teachings and prescriptions in this regard lead to its alleviation as far as possible in the short term, and, in the longer term, conduce to its progressive suppression. To abolish it would have been impossible in a world in which it was generally practiced by all the states which bordered on the new Muslim empire, and in which the idea of challenging the principle itself had not occurred to anyone. It was the custom to enslave prisoners of war -- when these were not simply massacred -- and the Islamic state would have put itself at a grave disadvantage vis-a-vis its enemies had it not reciprocated to some extent. By guaranteeing them humane treatment, and various possibilities of subsequently releasing themselves, it ensured that a good number of combatants in the opposing armies preferred captivity at the hands of Muslims to death on the field of battle.
It should be very clearly underlined that the slavery once practiced in the Muslim world cannot be compared to the form it had assumed -- for instance -- in the Roman Empire. Islamic legislation subjected slaveowners to a set of precise obligations, first among which was the slave's right to life, for, according to a hadith, 'Whoever kills his slave shall be killed by us'. In consequence, the murder of a slave was punished like that of a free man.
There are many other hadiths which define Islam's true attitude in this regard. The Prophet said: 'Your slaves are your brethren; therefore whoever has a brother who depends upon him must feed and clothe him in the way he feeds and clothes himself; and should not impose upon him tasks which exceed his capacity; should you ask them to do such things, then you are obliged to help them.' The Sharia takes this injunction, among many others, into account when defining the responsibilities and duties of slaveholders.
There is another teaching which enjoins respect for the human dignity of slaves: 'Let none of you say, "This man, or this woman, is my slave". He must rather say: "This is my man, and this my woman."' Putting into relief the provisional character of social ties and the authority exercised by slaveowners over their slaves, the Prophet said: 'It is true that God has made you their masters, but, had He so wished, He could equally well have made you their slaves.'
To manumit a slave has always been regarded as one of the most meritorious of all acts, and many passages of the Qur'an recommend or even require it, particularly as a means of expiation for serious faults. Traditional legislation lays down the methods of voluntary liberation of slaves by their masters (itq), and there were very many Muslims who observed these, especially at the end of their lives, so as not to die and appear before God without having given full freedom to the human beings placed in their power during their earthly lives.
Additionally, slaves had the ability to enfranchise themselves at their own initiative, without waiting passively for the goodwill of their masters: the procedure known as mukataba allowed them to buy their own freedom with sums which they saved from their work, and which the state frequently augmented with advances -- a measure which the slaveowner had no right to oppose. In contrast to the situation under Roman law, slaves were not deprived of the legal ability to exercise their rights and to appeal to a judge against their masters in all cases of illegal treatment.
Besides domestic slavery, which was generally imbued with a patriarchal character, there also existed a form of military slavery, which was frequently employed by princes in need of recruits, especially for their personal guards. This situation had the effect of conferring an often considerable influence and power on men of servile condition or origin, and some of these became the founders of great and illustrious dynasties such as the Tulunids and Mamlukes of Egypt.
The object of a prosperous commercial sector, which under the Abbasid Empire was often the speciality of non-Muslims, particularly Byzantine and Venetian Christians, and Jews, slavery gradually declined in importance until, at the beginning of the present century, it was confined to a few survivals which have now disappeared entirely. Thanks to the strict traditional controls which have always regulated the practice, it would be difficult to deny that social conditions were remarkably humane during the great periods of Muslim civilization, and that these, moreover, were in conformity with the 'egalitarian' spirit of Islam, which, in a hadith, teaches that 'the blackest of Abyssinians' is superior to most noble of Qurai****es, if he has more faith. -- p. 104 - 107
David Hecht, "Slavery" African Style
Howard Zinn, Declarations of Independence
The idea that entered Western consciousness several centuries ago, that black people are less than human, made possible the Atlantic slave trade, during which perhaps 40 million people died. -- p. 1
Sayyid Sa'eed Akhtar Rizvi, Slavery From Islamic and Christian Perspectives
Among all the religions it was only Islam that attacked the very foundations of this evil. -- preface
Sylviane A. Diouf, Servants of Allah: African Muslims Enslaved in the Americas
Author asserts that Islam was the first revealed religion followed by African slaves, and describes their struggle in upholding Islamic practices.
Fi amanillah.