Exodus 12:17-20

17This will be the Feast of Flat Bread, when you eat bread with no yeast in it. You will remember that I brought you all out of the country of Egypt on this day. You marched out like an army, family by family! That is why you must enjoy this day as a special day, for all time. This is a rule that you must always obey.

18In the first month of each year, you must eat bread without yeast in it. Do this from the evening of the 14th day until the evening of the 21st day.

19For those seven days, you must not have any yeast in your houses. Whoever eats anything with yeast in it will no longer belong to my people, the Israelites. Everyone must obey these rules, those who live among you as strangers, as well as those who have been born in your land.

20Eat nothing that has yeast in it. Whatever country you live in, you must eat bread without yeast in it.’