Exodus 13:14-16

“And in the future, your children will ask you, ‘What does all this mean?’ Then you will tell them, ‘With the power of his mighty hand, the LORD brought us out of Egypt, the place of our slavery. Pharaoh stubbornly refused to let us go, so the LORD killed all the firstborn males throughout the land of Egypt, both people and animals. That is why I now sacrifice all the firstborn males to the LORD—except that the firstborn sons are always bought back.’ This ceremony will be like a mark branded on your hand or your forehead. It is a reminder that the power of the LORD’s mighty hand brought us out of Egypt.”