Leviticus 25:40-43, 45

They are to be treated as hired workers or temporary residents among you; they are to work for you until the Year of Jubilee. Then they and their children are to be released, and they will go back to their own clans and to the property of their ancestors. Because the Israelites are my servants, whom I brought out of Egypt, they must not be sold as slaves. Do not rule over them ruthlessly, but fear your God.

You may also buy some of the temporary residents living among you and members of their clans born in your country, and they will become your property.