Exodus 12:37-39

37And the people of Israel journeyed from Rameses to Succoth, about six hundred thousand men on foot, besides women and children.

38A mixed multitude also went up with them, and very much livestock, both flocks and herds.

39And 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.