Exodus 13:14-16

14In the future, when your son asks you ‘What is this?’ you are to tell him, ‘With a mighty hand the Lord brought us out from Egypt, from the land of slavery.

15When Pharaoh stubbornly refused to release us, the Lord killed all the firstborn in the land of Egypt, from the firstborn of people to the firstborn of animals. That is why I am sacrificing to the Lord the first male offspring of every womb, but all my firstborn sons I redeem.’

16It will be for a sign on your hand and for frontlets on your forehead, for with a mighty hand the Lord brought us out of Egypt.”