Exodus 12:25-27

It will come to pass when you come to the land which the LORD will give you, just as He promised, that you shall keep this service. And it shall be, when your children say to you, ‘What do you mean by this service?’ that you shall say, ‘It is the Passover sacrifice of the LORD, who passed over the houses of the children of Israel in Egypt when He struck the Egyptians and delivered our households.’ ” So the people bowed their heads and worshiped.