Deuteronomy 16:3-4

Thou shalt eate no leauened bread with it: but seuen dayes shalt thou eate vnleauened bread therewith, euen the bread of tribulation: for thou camest out of the land of Egypt in haste, that thou maist remember ye day whe thou camest out of the land of Egypt, all the dayes of thy life.

And there shalbe no leauen seene with thee in all thy coastes seuen dayes long: neither shall there remaine the night any of the flesh vntil the morning which thou offeredst ye first day at euen.