Deuteronomy 16:3

Thou shalt eat no leavened bread with it, Exodus 12-15; seven days shalt thou eat unleavened bread therewith, even the bread of affliction, to remind the people of the oppression which they suffered in Egypt and of the suddenness of the delivery; for thou camest forth out of the land of Egypt in haste, the Egyptians almost thrusting them forth, Exodus 12:39; that thou mayest remember the day when thou camest forth out of the land of Egypt all the days of thy life.