Exodus 12:17-19

Amplified Bible

¹⁷ You shall also observe the Feast of Unleavened Bread, because on this very day I brought your hosts [grouped according to tribal armies] out of the land of Egypt; therefore you shall observe this day throughout your generations as an ordinance forever. ¹⁸ In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, [and continue] until the twenty-first day of the month at evening. ¹⁹ Seven days no leaven shall be found in your houses; whoever eats what is leavened shall be cut off and excluded from [the atonement made for] the congregation of Israel, whether a stranger or native-born.^(A)