Leviticus 25:43

41Then he shall go out from you, he and his children with him, and shall return to his own family, and to the possession of his fathers.

42For they are my servants, whom I brought out of the land of Egypt. They shall not be sold as slaves.

43You shall not rule over him with harshness, but shall fear your God.

44“‘As for your male and your female slaves, whom you may have from the nations that are around you, from them you may buy male and female slaves.

45Moreover, of the children of the aliens who live among you, of them you may buy, and of their families who are with you, which they have conceived in your land; and they will be your property.