Thematic Bible: Firstborn set apart as a

You are to put on one side for the Lord every mother's first male child, the first-fruit of her body, and the first young one of every beast; every male is holy to the Lord. And for the young of an ass you may give a lamb in payment, or if you will not make payment for it, its neck is to be broken; but for all the first sons among your children, let payment be made. And when your son says to you in time to come, What is the reason for this? say to him, By the strength of his hand the Lord took us out of Egypt, out of the prison-house: read more.
And when Pharaoh made his heart hard and would not let us go, the Lord sent death on all the first sons in Egypt, of man and of beast: and so every first male who comes to birth is offered to the Lord; but for all the first of my sons I give a price. And this will be for a sign on your hand and for a mark on your brow: for by the strength of his hand the Lord took us out of Egypt.