Exodus 12:18-20

181In 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. 192Seven days there shall be no leaven found in your houses; for whoever eats what is leavened, that 34person shall be cut off from the congregation of Israel, whether he is an alien or a native of the land. 20You shall not eat anything leavened; in all your dwellings you shall eat unleavened bread.’”