Leviticus 25:40-43, 45

he shall be with you as a hired worker and as a sojourner. He shall serve with you until the year of the jubilee. Then he shall go out from you, he and his children with him, and go back to his own clan and return to the possession of his fathers. For they are my servants, whom I brought out of the land of Egypt; they shall not be sold as slaves. You shall not rule over him ruthlessly but shall fear your God.

You may also buy from among the strangers who sojourn with you and their clans that are with you, who have been born in your land, and they may be your property.