Exodus 34:18-21

18“You must keep the Feast of Unleavened Bread. For seven days you must eat bread made without yeast, as I commanded you; do this at the appointed time of the month Abib, for in the month Abib you came out of Egypt.

19“Every firstborn of the womb belongs to me, even every firstborn of your cattle that is a male, whether ox or sheep.

20Now the firstling of a donkey you may redeem with a lamb, but if you do not redeem it, then break its neck. You must redeem all the firstborn of your sons. “No one will appear before me empty-handed.

21“On six days you may labor, but on the seventh day you must rest; even at the time of plowing and of harvest you are to rest.