Deuteronomy 16:6 (KJV)

And there shall be no leavened bread seen with thee in all thy coast seven days; neither shall there any thing of the flesh, which thou sacrificedst the first day at even, remain all night until the morning.

Thou mayest not sacrifice the passover within any of thy gates, which the Lord thy God giveth thee:

But at the place which the Lord thy God shall choose to place his name in, there thou shalt sacrifice the passover at even, at the going down of the sun, at the season that thou camest forth out of Egypt.

And thou shalt roast and eat it in the place which the Lord thy God shall choose: and thou shalt turn in the morning, and go unto thy tents.

Six days thou shalt eat unleavened bread: and on the seventh day shall be a solemn assembly to the Lord thy God: thou shalt do no work therein.