Deuteronomy 15:18 in the King James Version
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.
Context
17 then you shall take an awl, and thrust it through his ear to the door, and he shall be your servant forever. Also to your female servant you shall do likewise.
18 It shall not seem hard to you when you let him go free from you, for he has been double the value of a hired hand as he served you six years. The LORD your God will bless you in all that you do.
19 You shall dedicate all the firstborn males that are born of your herd and of your flock to the LORD your God. You shall do no work with the firstborn of your herd, nor shear the firstborn of your flock.