Deuteronomy 15:18

“It shall not seem hard to thee when thou sendest him away free from thee, etc.] He should not grudge him his liberty, nor what he gives to him when he dismisses him: for he hath been worth a double hired servant to thee in serving thee six years; since a hired servant a man is obliged to pay him wages for his work, besides his food, whereas a bondservant received no wages. Aben Ezra remarks, that this proves that a man might not hire himself for more than three years; or however, whereas a hired servant was sometimes hired for so many years, and this is the longest time of any we read of, a servant serving his master six years, his service must be worth double the service of an hired…”

“he hath been worth a double hired servant to thee--that is, he is entitled to double wages because his service was more advantageous to you, being both without wages and for a length of time, whereas hired servants were engaged yearly (Lev 25:53), or at most for three years (Isa 16:14).”

“The commands here are repeated from Exodus 21:2-6, with amplifications relative to the maidservant Deuteronomy 15:12 and to the making (Deuteronomy 15:13 ff) liberal provision for launching the freedman on an independent course of life. The release of the servant is connected with the sabbatical principle though not with the sabbatical year. It is noteworthy also that the prospect of a gift of this sort, the amount of which was left to the master’s discretion, would be likely to encourage diligence and faithfulness during the years of servitude. Deuteronomy 15:18 He hath been worth a double hired servant to thee, in serving thee six years - “i. e.” such a servant has earned twice as much as…”

“15:18 worth double the wages: Because a bondservant worked all day, every day, his output was more than that of a day laborer, who merely put in his shift.”

“shall not: Deu 15:10 a double: Isa 16:14, Isa 21:16; Luk 17:7, Luk 17:8 Deuteronomy 15:19”

“If, on the other hand, the servant (or maid) wished to be set free, the master was not to think it hard; "for the double of the wages of a day-labourer he has earned for thee for six years," i.e., not "twice the time of a day-labourer, so that he had really deserved twice the wages" (Vatablius, Ad. Osiander, J. Gerhard), for it cannot be proved from Isa 16:14, that a day-labourer generally hired himself out for three years; nor yet, "he has been obliged to work much harder than a day-labourer, very often by night as well as day" (Clericus, J. H. Michaelis, Rosenmller, Baumgarten); but simply, "he has earned and produced so much, that if you had been obliged to keep a day-labourer in his…”