Leviticus 25:40-43, 45

but he is to be with you as a hired man, as if he were a temporary resident; he shall serve with you until the Year of Jubilee, and then he shall leave you, he and his children with him, and shall go back to his own family and return to the property of his fathers. For the Israelites are My servants whom I brought out of the land of Egypt; they shall not be sold in a slave sale. [1 Cor 7:23] You shall not rule over him with harshness (severity, oppression), but you are to fear your God [with profound reverence]. [Eph 6:9; Col 4:1]

Moreover, from the children of the strangers who live as aliens among you, from them you may buy slaves and from their families who are with you, whom they have produced in your land; they may become your possession.