Leviticus 25:51-55
25:51 If there are still many years, in keeping with them he must refund most of the cost of his purchase for his redemption,
25:52 but if only a few years remain until the jubilee, he must calculate for himself in keeping with the remaining years and refund it for his redemption.
25:53 He must be with the one who bought him like a yearly hired worker. The one who bought him must not rule over him harshly in your sight.
25:54 If, however, he is not redeemed in these ways, he must go free in the jubilee year, he and his children with him,
25:55 because the Israelites are my own servants; they are my servants whom I brought out from the land of Egypt. I am the Lord your God.