Deuteronomy 15:18; Deuteronomy 24:14

18 It shall not seem hard unto thee, when thou sendest him away free from thee; for he hath been worth a double hired servant to thee, in serving thee six years: and the LORD thy God shall bless thee in all that thou doest.

14 Thou shalt not oppress an hired servant that is poor and needy, whether he be of thy brethren, or of thy strangers that are in thy land within thy gates: