Leviticus 25:42

40But as an hired servant, and as a sojourner, he shall be with thee, and shall serve thee unto the year of jubile.

41And then shall he depart from thee, both he and his children with him, and shall return unto his own family, and unto the possession of his fathers shall he return.

42For they are my servants, which I brought forth out of the land of Egypt: they shall not be sold as bondmen.

43Thou shalt not rule over him with rigour; but shalt fear thy God.

44Both thy bondmen, and thy bondmaids, which thou shalt have, shall be of the heathen that are round about you; of them shall ye buy bondmen and bondmaids.