Leviticus 25:43-45

⁴³You shall not rule over him with harshness, but shall fear your God.

⁴⁴“‘As for your male and your female slaves, whom you may have from the nations that are around you, from them you may buy male and female slaves.

⁴⁵Moreover, of the children of the aliens who live amongst you, of them you may buy, and of their families who are with you, which they have conceived in your land; and they will be your property.