Exodus 12:8, 18, 34, 39

On this night they must roast the lamb over a fire. They must eat it with bitter herbs and bread made without yeast.

In the first month of the year you are to eat bread made without yeast, from the evening of the fourteenth day until the evening of the twenty-first day.

So the people took their dough before the yeast was added. They wrapped the bowls for making dough in clothing and carried them on their shoulders.

The Israelites used the dough they had brought out of Egypt to bake loaves of bread without yeast. The dough had no yeast in it, because they had been rushed out of Egypt and had no time to get food ready for their trip.