So you shall observe the Feast of Unleavened Bread, for on this same day I will have brought your armies out of the land of Egypt. Therefore you shall observe this day throughout your generations as an everlasting ordinance.
Exodus 12:17
Surrounding context
12:16 On the first day there shall be a holy convocation, and on the seventh day there shall be a holy convocation for you. No manner of work shall be done on them; but that which everyone must eat--that only may be prepared by you.
12:17 So you shall observe the Feast of Unleavened Bread, for on this same day I will have brought your armies out of the land of Egypt. Therefore you shall observe this day throughout your generations as an everlasting ordinance.
12:18 In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, until the twenty-first day of the month at evening.