Leviticus 25:42-46

For they are My servants, whom I brought out of the land of Egypt; they shall not be sold as slaves. You shall not rule over him with rigor, but you shall fear your God. And as for your male and female slaves whom you may have—from the nations that are around you, from them you may buy male and female slaves. Moreover you may buy the children of the strangers who dwell among you, and their families who are with you, which they beget in your land; and they shall become your property. And you may take them as an inheritance for your children after you, to inherit them as a possession; they shall be your permanent slaves. But regarding your brethren, the children of Israel, you shall not rule over one another with rigor.