Exodus 12:28

26It will happen, when your children ask you, ‘What do you mean by this service?’

27that you shall say, ‘It is the sacrifice of the LORD’s Passover, who passed over the houses of the children of Israel in Egypt, when he struck the Egyptians, and spared our houses.’” The people bowed their heads and worshiped.

28The children of Israel went and did so; as the LORD had commanded Moses and Aaron, so they did.

29At midnight, the LORD struck all the firstborn in the land of Egypt, from the firstborn of Pharaoh who sat on his throne to the firstborn of the captive who was in the dungeon, and all the firstborn of livestock.

30Pharaoh rose up in the night, he, and all his servants, and all the Egyptians; and there was a great cry in Egypt, for there was not a house where there was not one dead.