Exodus 34:18-23

¹⁸The feast of unleavened bread shalt thou keep. Seven days thou shalt eat unleavened bread, as I commanded thee, at the time appointed in the month Abib; for in the month Abib thou camest out from Egypt. ¹⁹All that openeth the womb is mine; and all thy cattle that is male, the firstlings of cow and sheep. ²⁰And the firstling of an ass thou shalt redeem with a lamb: and if thou wilt not redeem it, then thou shalt break its neck. All the first-born 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 plowing time and in harvest thou shalt rest. ²²And thou shalt observe the feast of weeks, [even] of the first-fruits of wheat harvest, and the feast of ingathering at the year`s end. ²³Three times in the year shall all thy males appear before the Lord Jehovah, the God of Israel.