Levítico 25:50

50 They and their buyer are to count the time from the year they sold themselves up to the Year of Jubilee. The price for their release is to be based on the rate paid to a hired worker for that number of years.

50 And he shall reckon with him that bought him from the year that he sold himself to him unto the year of jubilee: and the price of his sale shall be according unto the number of years; according to the time of a hired servant shall he be with him.