Leviticus 25:45; Leviticus 25:46

45 You may also buy from among the strangers who sojourn with you and their clans that are with you, who have been born in your land, and they may be your property.

46 You may bequeath them to your sons after you to inherit as a possession forever. You may make slaves of them, but over your brothers the people of Israel you shall not rule, one over another ruthlessly.