The Bible talks about slavery a lot and it is too a large subject to go into here but a few observations are called for.
There are two forms of slavery. Both are about someone owning someone else but one is where the slave is mistreated and traded as a piece of flesh (which the Bible condemns) and the other is a slave that is taken into the family and is cared for and often loved. With this second type, if they were Jewish, it would be because they had sold themselves into slavery because of hardship that had befallen them but they had to be set free on the seventh year. The Jews could have slaves from non Jewish tribes but they were still required to treat them fairly.
Slavery was something that already existed in the ancient world when the Law of Moses was laid down and the law neither encourages it or condemns it but it does have much to say about how slaves are treated. The difference between the Bible and Islam on slavery is stark. Muhammad had slaves, traded them and taught that it was okay to take them as sex slaves (even if they were already married to another slave). Again Deedat is trying to justify the practice in Islam by trying to point to the Bible.
Christianity has been a big force in the outlawing of slavery and was the main reason that western nations went on to outlaw the practice, not only in their nations but even going as far as using their gunships to intersect slave ships at sea. In later times through history there have been some Muslims who fought against slavery but the large majority were Christians.
The Bible tells us that we are all slaves. In the Gospel of John we read these words “Jesus replied, “Very truly I tell you, everyone who sins is a slave to sin.””(John 8:34). Jesus is the only one who can free us from the bondage of sin. He does this by purchasing us for himself, so strictly people we are still slaves but now to God. The musician Bob Dylan summed it up like this in one of his songs, “You gotta serve somebody – it may be the Devil and it may be the Lord, but you still gotta serve somebody”[5].