Leviticus 25:44-46

“The male and female slaves which you have are to come from the surrounding nations; you are permitted to buy slaves from them. You may also buy the children of foreign workers who are living among you temporarily and from their clans which are living among you and have been born in your land. They become your property. You may will them to your children as property and make them slaves for life. But you must not tyrannize your brother Israelites.