Leviticus 25:44-46

44And as for thy bondmen, and thy bondmaids, which thou shalt have; of the nations that are round about you, of them shall ye buy bondmen and bondmaids.

45Moreover of the children of the strangers that do sojourn among you, of them shall ye buy, and of their families that are with you, which they have begotten in your land: and they shall be your possession.

46And ye shall make them an inheritance for your children after you, to hold for a possession; of them shall ye take your bondmen for ever: but over your brethren the children of Israel ye shall not rule, one over another, with rigour.