Leviticus 25:27, 51-52

then he shall calculate the years since its sale and refund the balance to the man to whom he sold it, and so return to his [ancestral] property. [1 Kin 21:2, 3]

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. 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.