Exodus 34:19

17Thou shalt make thee no molten gods.

18The feast of unleavened bread shalt thou keep. Seven days thou shalt eat unleavened bread, as I commanded thee, in the time of the month Abib: for in the month Abib thou camest out from Egypt.

19All that openeth the matrix is mine; and every firstling among thy cattle, whether ox or sheep, that is male.

20But the firstling of an ass thou shalt redeem with a lamb: and if thou redeem him not, then shalt thou break his neck. All the firstborn of thy sons thou shalt redeem. And none shall appear before me empty.

21Six days thou shalt work, but on the seventh day thou shalt rest: in earing time and in harvest thou shalt rest.