Slaves are booty, or a gift, Allah gives, Koran 33:50: O Prophet! we allow thee thy wives whom thou hast dowered, and the slaves whom thy right hand possesseth out of the booty which God hath granted thee.
Slaves are not equal to free people, Koran 16:72: God maketh comparison between a slave the property of his lord, who hath no power over anything, and a free man whom we have ourselves supplied with goodly supplies, and who giveth alms therefrom both in secret and openly. Shall they be held equal? No: praise be to God!
You are permitted to have sex with your slaves, Koran 33:52: It is not permitted thee to take other wives hereafter, nor to change thy present wives for other women, though their beauty charm thee, except slaves whom thy right hand shall possess, And God watcheth all things.
Koran 4:24: Forbidden to you (for sex) also are married women, except those who are in your hands as slaves: This is the law of God for you.
You do not have to control your desires with your slaves, Koran 70:30: And who control their desires, Save with their wives or the slaves whom their right hands have won, for there they shall be blameless.
You may marry your slaves, Koran 4:25: And whoever of you is not rich enough to marry free believing women, then let him marry such of your believing maidens as have fallen into your hands as slaves; God well knoweth your faith.
Muhammadís interpretation, Then I put on my clothes and went to the residence of Allahís Messenger (peace_be_upon_him), and behold, he was staying in an upper room of his to which he ascended by a ladder, and a black slave of Allahís Messenger (peace_be_upon_him) was (sitting) on the first rung (Hadith, Sahih alBukhari 6.435).