Exodus 12:40 (KJV)

And a mixed multitude went up also with them; and flocks, and herds, even very much cattle.

And they baked unleavened cakes of the dough which they brought forth out of Egypt, for it was not leavened; because they were thrust out of Egypt, and could not tarry, neither had they prepared for themselves any victual.

Now the sojourning of the children of Israel, who dwelt in Egypt, was four hundred and thirty years.

And it came to pass at the end of the four hundred and thirty years, even the selfsame day it came to pass, that all the hosts of the Lord went out from the land of Egypt.

It is a night to be much observed unto the Lord for bringing them out from the land of Egypt: this is that night of the Lord to be observed of all the children of Israel in their generations.