And יהוה spoke to Mosheh and to Aharon in the land of Mitsrayim, saying,...
“Speak to all the congregation of Yisra’ĕl..., Let the lamb be a perfect one...,
And the blood shall be a sign for you on the houses where you are. And when I see the blood, I shall pass over you..., And this day shall become to you a remembrance. And you shall observe it as a festival to יהוה throughout your generations – observe it as a festival, an everlasting law.
Seven days you shall eat unleavened bread. Indeed on the first day you cause leaven to cease from your houses. For whoever eats leavened bread from the first day until the seventh day, that being shall be cut off from Yisra’ĕl.
And on the first day is a set-apart gathering, and on the seventh day you have a set-apart gathering." (Exodus 12:1-16)