Exodus 12:40-42

40Now the period of time the children of Israel lived in Egypt was four hundred and thirty years.

41At the end of the four hundred and thirty years, to that very day, all the hosts of the Lord [gathered into tribal armies] left the land of Egypt.

42It is a night of watching to be observed for the Lord for having brought them out of the land of Egypt; this [same] night is for the Lord, to be observed and celebrated by all the Israelites throughout their generations.