Leviticus 25:44-46

⁴⁴But thy bond-man, and thy bond-woman that shall remain thine, shall be of the nations that are round about you; of them may ye buy bond-man and bond-woman.

⁴⁵And also of the children of the strangers that sojourn with you, of them may ye buy, and of their families that are with you, which they have begotten in your land; and they shall remain to you as a possession.

⁴⁶And ye may transfer them as an inheritance for your children after you, to inherit them for a possession; you may hold them to service for ever; but over your brethren the children of Israel, one over the other, ye shall not rule with rigor.