Exodus 12:37-39

The Israelites traveled from Rameses to Succoth. There were about six hundred thousand men walking, not including the women and children. Many other people who were not Israelites went with them, as well as a large number of sheep, goats, and cattle. 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.