The concept of treating the slaves in Islam is Quite different from what people understand, it is not that which was  practiced in ancient civilization including Judaism and Christianity.

(1)In Islam, slaves are to be fed the same food their master eat and even to be clothed as their master are.

  The prophet says

" Those slaves are your brothers, only God gave you an upper hand over them. So let that who has his brother (i.e. slave) under him give him the same food he himself eats, and the same clothing as he himself wears. The master may not give his brother a task that is beyond his ability. If he does give him such task, let him lend him a hand.".

(2)Slaves are to be treated gently and with high dignity

Abu Hurairah narrates that the Prophet of Repentance (i.e. Prophet Muhammad) said :

          " Any one who slanders his slave with adultery, and it is a false charge, will receive on the Day of Resurrection the same punishment his slave would have received in the world had the charge been true."

(3) A slave can lead his master in prayer and even he can lead armies

Aishah had a slave who led her prayer.

The prophet says" obey to your leader even if he is a black slave."

The Prophet, peace and blessings of God be on him, again and again ordered kindness to the slaves. For instance, when the captives taken in the Battle of Badr were distributed , he directed them : "Be kind to your captives."