Leviticus 25:48

You may make them an inheritance for your children after you, to hold for a possession; of them may you take your slaves forever: but over your brothers the children of Israel you shall not rule, one over another, with harshness.

If an alien or temporary resident with you becomes rich, and your brother beside him has grown poor, and sells himself to the stranger or foreigner living among you, or to a member of the stranger's family;

or his uncle, or his uncle's son, may redeem him, or any who is a close relative to him of his family may redeem him; or if he has grown rich, he may redeem himself.

He shall reckon with him who bought him from the year that he sold himself to him to the Year of Jubilee: and the price of his sale shall be according to the number of years; according to the time of a hired servant shall he be with him.