Exodus 12:8, 18, 34, 39

And they shall eat the flesh in that night, roast with fire, and unleavened bread; and with bitter herbs they shall eat it.

In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one and twentieth day of the month at even.

And the people took their dough before it was leavened, their kneadingtroughs being bound up in their clothes upon their shoulders.

And they baked unleavened cakes of the dough which they brought forth out of Egypt, for it was not leavened; because they were thrust out of Egypt, and could not tarry, neither had they prepared for themselves any victual.