Deut 16:1-3

1Observe the month  of Abib by keeping the passover for the Lord your God, for in the month of Abib the Lord your God brought you out of Egypt by night. 2You shall offer the passover sacrifice for the Lord your God, from the flock and the herd, at the place that the Lord will choose as a dwelling for his name. 3You must not eat with it anything leavened. For seven days you shall eat unleavened bread with it—the bread of affliction—because you came out of the land of Egypt in great haste, so that all the days of your life you may remember the day of your departure from the land of Egypt.