Exodus 13:14-16

14And it shall be when thy son asketh thee in time to come, saying, What is this? that thou shalt say to him, By strength of hand the LORD brought us out from Egypt, from the house of bondage:1 15And it came to pass, when Pharaoh would hardly let us go, that the LORD slew all the firstborn in the land of Egypt, both the firstborn of man, and the firstborn of beasts: therefore I sacrifice to the LORD all that openeth the womb, being males; but all the firstborn of my children I redeem. 16And it shall be for a token upon thy hand, and for frontlets between thy eyes: for by strength of hand the LORD brought us forth out of Egypt.