Exodus 12:18-20

¹⁸In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, and so until the twenty-first day of the month at evening. ¹⁹For seven days no leaven shall be found in your houses; for if any one eats what is leavened, that person shall be cut off from the congregation of Israel, whether he is a sojourner or a native of the land. ²⁰You shall eat nothing leavened; in all your dwellings you shall eat unleavened bread."