Leviticus 25:50-52

Amplified Bible

⁵⁰ Then he [or his redeemer] shall calculate with his purchaser from the year when he sold himself to the purchaser to the Year of Jubilee, and the [original] price of his sale shall be adjusted according to the number of years. The time he was with his owner shall be considered as that of a hired man. ⁵¹ If there are still many years [before the Year of Jubilee], in proportion to them he must refund [to the purchaser] part of the price of his sale for his redemption and release. ⁵² And if only a few years remain until the Year of Jubilee, he shall so calculate it with him. He is to refund the proportionate amount for his release.