12 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. 13 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. 14 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: 15 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.
Matthew Henry's Commentary on Exodus 13:12-15
Commentary on Exodus 13:11-16
(Read Exodus 13:11-16)
The firstlings of beast not used in sacrifice, were to be changed for others so used, or they were to be destroyed. Our souls are forfeited to God's justice, and unless ransomed by the sacrifice of Christ, will certainly perish. These institutions would continually remind them of their duty, to love and serve the Lord. In like manner, baptism and the Lord's supper, if explained and attended to, would remind us, and give us occasion to remind one another of our profession and duty.