Charles Ellicott Commentary Leviticus 25:50-52

"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. If there be yet many years, according unto them he shall give back the price of his redemption out of the money that he was bought for. And if there remain but few years unto the year of jubilee, then he shall reckon with him; according unto his years shall he give back the price of his redemption." — Leviticus 25:50-52 (ASV)

And he shall reckon with him. —That is, either the man himself when he is able to redeem himself, or his relatives. The authorities during the Second Temple rightly point out that this passage instructs the Hebrew to treat the gentile master fairly by duly compensating and settling the payment for the number of years he still has to serve until the Jubilee, and to take no advantage of the idolater.