Leviticus 25:51-53

Thomson(i) 51 And if any one hath many years to serve, for them he shall pay the rates of redemption, on account of the money paid for him; 52 and if but few years remain to the year of release, he shall settle with him according to those years, and pay the rates of his redemption. 53 As a servant hired from year to year, he shall be with him; and thou shalt not suffer him to be oppressed with labour in thy sight.