Exodus 12:18-20

¹⁸In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one and twentieth day of the month at even. ¹⁹Seven days shall there be no leaven found in your houses: for whosoever eateth that which is leavened, even that soul shall be cut off from the congregation of Israel, whether he be a stranger, or born in the land. ²⁰Ye shall eat nothing leavened; in all your habitations shall ye eat unleavened bread.