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.

Read Exodus 12:42 Using Other Translations

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.
It was a night of watching by the LORD, to bring them out of the land of Egypt; so this same night is a night of watching kept to the LORD by all the people of Israel throughout their generations.
On this night the LORD kept his promise to bring his people out of the land of Egypt. So this night belongs to him, and it must be commemorated every year by all the Israelites, from generation to generation.