Deuteronomy 15:18
"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."
Cross References (ranked by relevance)
Isaiah 21:16
For thus hath the LORD said unto me, Within a year, according to the years of an hireling, and all the glory of Kedar shall fail:
Isaiah 16:14
But now the LORD hath spoken, saying, Within three years, as the years of an hireling, and the glory of Moab shall be contemned, with all that great multitude; and the remnant shall be very small and feeble.