Leviticus 25:40-43

25:40 He must be with you as a hired worker, as a resident foreigner; he must serve with you until the year of jubilee, 25:41 but then he may go free, he and his children with him, and may return to his family and to the property of his ancestors. 25:42 Since they are my servants whom I brought out from the land of Egypt, they must not be sold in a slave sale. 25:43 You must not rule over him harshly, but you must fear your God.

Leviticus 25:45

25:45 Also you may buy slaves from the children of the foreigners who reside with you, and from their families that are with you, whom they have fathered in your land, they may become your property.