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.
Leviticus 25:45
Surrounding context
25:44 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.
25:45 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.
25:46 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.