Slavery in the OT times is not what we think of it today, with the atrocities of the african slaves and all. It had to do with the financial structure of the culture. If you were indebted to someone, you could pay them back by being their servant, i.e. slave, but it was a respectful relationship where the servant had a choice to stay or leave when the debt was paid, but usually stayed with the family for financial reasons.
(Deut 15:12-18) If a fellow Hebrew, a man or a woman, sells himself to you and serves you six years, in the seventh year you must let him go free.
13 And when you release him, do not send him away empty-handed.
14 Supply him liberally from your flock, your threshing floor and your winepress. Give to him as the LORD your God has blessed you.
15 Remember that you were slaves in Egypt and the LORD your God redeemed you. That is why I give you this command today.
16 But if your servant says to you, "I do not want to leave you," because he loves you and your family and is well off with you,
17 then take an awl and push it through his ear lobe into the door, and he will become your servant for life. Do the same for your maidservant.
18 Do not consider it a hardship to set your servant free, because his service to you these six years has been worth twice as much as that of a hired
hand. And the LORD your God will bless you in everything you do.
Hope that helps,
Penn
Mohammed- 'My teachings lead to the attainment of truth'
Buddha- 'The truth has been revealed to me'
Jesus- 'I am the truth'