Leviticus 25:47-55

And if a stranger or sojourner with thee be waxed rich, and thy brother be waxed poor beside him, and sell himself unto the stranger or sojourner with thee, or to the stock of the stranger’s family; after that he is sold he may be redeemed: one of his brethren may redeem him; or his uncle, or his uncle’s son, may redeem him, or any that is nigh of kin unto him of his family may redeem him; or if he be waxed rich, he may redeem himself. And he shall reckon with him that bought him from the year that he sold himself to him unto the year of jubilee: and the price of his sale shall be according unto the number of years; according to the time of a hired servant shall he be with him. If there be yet many years, according unto them he shall give back the price of his redemption out of the money that he was bought for. And if there remain but few years unto the year of jubilee, then he shall reckon with him; according unto his years shall he give back the price of his redemption. As a servant hired year by year shall he be with him: he shall not rule with rigor over him in thy sight. And if he be not redeemed by these means, then he shall go out in the year of jubilee, he, and his children with him. For unto me the children of Israel are servants; they are my servants whom I brought forth out of the land of Egypt: I am Jehovah your God.