Exodus 12:37-39

37Then Bnei-Yisrael journeyed from Rameses to Succoth, about 600,000 men on foot, as well as children.

38Also a mixed multitude went up with them, along with the flocks, herds and heavy livestock.

39They had baked matzot cakes from the dough that they brought out of Egypt. It had no hametz, because they were thrust out of Egypt and could not delay, so they had not made provisions for themselves.