Exodus 12:8, 18, 34, 39

They shall eat the flesh that night, roasted on the fire; with unleavened bread and bitter herbs they shall eat it.

In the first month, from the fourteenth day of the month at evening, you shall eat unleavened bread until the twenty-first day of the month at evening.

So the people took their dough before it was leavened, their kneading bowls being bound up in their cloaks on their shoulders.

And they baked unleavened cakes of the dough that they had brought out of Egypt, for it was not leavened, because they were thrust out of Egypt and could not wait, nor had they prepared any provisions for themselves.