Exodus 12:25-29

When you enter the land which the Lord will give you, as He has promised, you shall keep this rite.

And when your children say to you, ‘What does this rite mean to you?’

then you shall say, ‘It is a Passover sacrifice to the Lord because He passed over the houses of the sons of Israel in Egypt when He struck the Egyptians, but spared our homes.’ ” And the people bowed low and worshiped.

Then the sons of Israel went and did so; just as the Lord had commanded Moses and Aaron, so they did.

Now it came about at midnight that 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 cattle.