First of all, we would like to stress that Islam caters for rights of every creature. It urges a Muslim to show good and kind treatment to anyone under his/her control; he should neither maltreat him or her nor should he subject him/her to any form of exploitation.
Islam totally objects and fights all forms of slavery. The focus of Islam in all its teachings and rites was to eradicate this prevailing practice. Now, slavery has been abolished by international conventions, and this goes in line with the goals of Islam.
Dr. TahaJaber Al-`Alwani, president of the Graduate School of Islamic and Social Sciences and president of the Fiqh Council, states: When Allah created human beings, He created them to be free and to be vicegerents on the earth. Slavery is something that came from people who couldn’t understand the position of the human being and it was made, in the past, as a global phenomenon.

When Islam came, it tried to bring change to get the human being back to being free, as Allah has created us, by certain procedures. Those procedures of Islam went through without interference from the other nations or states who are non-Muslim states or nations. Maybe within the third century of Hijrah or the migration of the Prophet to Madinah, this phenomenon would have been over and disappeared. But as I mentioned, because it was a global phenomenon, that procedure which was established by Islam couldn’t go through and finish with this very bad phenomenon.

Now, al-hamdulillah all people have agreed to stop this phenomenon and stand up against it. With this, there is no way to go back to adopt this phenomenon again in any way, especially for Muslims, since they must protect the freedom of others and always be with their rights to be free servants of Allah only. We should remember when the Caliph `UmarIbn Al-Khattab (may Allah be pleased with him) said in a famous khutbah (speech or sermon) of his, “When did you make the people as slaves or servants of you while Allah, the Almighty, created them free!” This means that the Muslims from the very beginning advocated the freedom of all human beings and were against the oppression of free people by tyrants and dictator leaders.”

Having clarified the above, we would like to state that it was a war custom in the past to take men and women as captives and then turn them into slaves. Islam did not initiate it, rather, it was something in practice long ago before the advent of Islam. And when Islam came, it tried to eradicate this practice, bit by bit. So, it first restricted it to the reciprocal practice of war, in the sense that Muslims took war captives just as the enemies did with them.