Exodus 23:15

23:15 You are to observe the Feast of Unleavened Bread; seven days you must eat bread made without yeast, as I commanded you, at the appointed time of the month of Abib, for at that time you came out of Egypt. No one may appear before me empty-handed.

Exodus 34:18

34:18 “You must keep the Feast of Unleavened Bread. For seven days you must eat bread made without yeast, as I commanded you; do this at the appointed time of the month Abib, for in the month Abib you came out of Egypt.

Deuteronomy 16:1-3

The Passover-Unleavened Bread Festival

16:1 Observe the month Abib and keep the Passover to the Lord your God, for in that month he brought you out of Egypt by night. 16:2 You must sacrifice the Passover animal (from the flock or the herd) to the Lord your God in the place where he chooses to locate his name. 16:3 You must not eat any yeast with it; for seven days you must eat bread made without yeast, symbolic of affliction, for you came out of Egypt hurriedly. You must do this so you will remember for the rest of your life the day you came out of the land of Egypt.