Leviticus 25:39-42

If thy brother constrained by poverty, sell himself to thee: thou shalt not oppress him with the service of bondservants.

But he shall be as a hireling, and a sojourner: he shall work with thee until the year of the jubilee.

And afterwards he shall go out with his children: and shall return to his kindred and to the possession of his fathers.

For they are my servants, and I brought them out of the land of Egypt: let them not be sold as bondmen.