Exodus 12:40-42

40 Now the length of time the Israelite people lived in Egypta was 430 years.
41 At the end of the 430 years, to the very day, all the LORD’s divisions left Egypt.
42 Because the LORD kept vigil that night to bring them out of Egypt, on this night all the Israelites are to keep vigil to honor the LORD for the generations to come.