Leviticus 25:50-54

50He must calculate with the one who bought him the number of years from the year he sold himself to him until the jubilee year, and the cost of his sale must correspond to the number of years, according to the rate of wages a hired worker would have earned while with him.

51If there are still many years, in keeping with them he must refund most of the cost of his purchase for his redemption,

52but 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.

53He 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.

54If, however, he is not redeemed in these ways, he must go free in the jubilee year, he and his children with him,