Leviticus 25:44-46

44And as for thy bondman and thy handmaid whom thou shalt have — of the nations that are round about you, of them shall ye buy bondmen and handmaids.

45Moreover of the children of them that dwell as sojourners with you, of them may ye buy, and of their family that is with you, which they beget in your land, and they shall be your possession.

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