Leviticus 25:14-16

14If you make a sale to your neighbor or a purchase from him, you must not take advantage of each other. 15You are to buy from your neighbor according to the number of years since the last Jubilee; he is to sell to you according to the number of harvest years remaining. 16You shall increase the price in proportion to a greater number of years, or decrease it in proportion to a lesser number of years; for he is selling you a given number of harvests.