Exodus 13:15

15 When the king of Egypt was stubborn and refused to let us go, the Lord killed every first-born male in the land of Egypt, both human and animal. That is why we sacrifice every first-born male animal to the Lord, but buy back our first-born sons.

Exodus 13:15 Meaning and Commentary

Exodus 13:15

And it came to pass, when Pharaoh would hardly let us go
Showed great reluctance to it, and with difficulty was prevailed upon to dismiss them: that the Lord slew all the firstborn in the land of Egypt, both the
firstborn of men, and the firstborn of beast:
which he did in one night, making use of a destroying angel or angels for that purpose: therefore I sacrifice to the Lord all that openeth thee matrix, being
males;
that is, the firstborn of all clean creatures, as oxen, sheep, and goats: but all the firstborn of my children I redeem;
by paying five shekels apiece to the priest for them, as before observed; and this law continues to be observed with the Jews; the manner of which, as related by Leo Modena F9, is as follows,

``Thirty days being expired after the birth of the child, they call a priest to them; that is to say, one that is descended of the stock of Aaron, whom the father of the child pleaseth; and so, many people being gathered together at the time appointed, the father of the child bringeth before the priest, in a bowl or basin, a good quantity of gold and silver, and then they give him the child into his arms; the priest then calling the mother of it before him, saith unto her, mistress, is this your son? she answereth, yes; then, replies he, have you never had any child before, either male or female, or have miscarried anyone? she saith unto him, no; then doth the priest say, this child is mine, as being the firstborn; then turning himself toward the father, he asketh him, whether he will redeem it or not? who answereth him, saying, see, here is gold and silver, take your own price; then saith the priest unto him, you will redeem it then? the father answereth, I will redeem it; it shall be so then, saith the priest, this child is mine as being the firstborn, as it is written, ( Numbers 18:16 ) . I therefore take this in exchange and so he takes the sum of two French crowns, or thereabout, as he thinks good, and then delivers the child to his father and mother, and this day they make a feasting day.''
This custom was used in Christ's time, and was observed with respect to him, ( Luke 2:27 ) .
FOOTNOTES:

F9 History of the Jews, par. 4. c. 9. sect. 2.

Exodus 13:15 In-Context

13 but you must buy back from him every first-born male donkey by offering a lamb in its place. If you do not want to buy back the donkey, break its neck. You must buy back every first-born male child of yours.
14 In the future, when your son asks what this observance means, you will answer him, "By using great power the Lord brought us out of Egypt, the place where we were slaves.
15 When the king of Egypt was stubborn and refused to let us go, the Lord killed every first-born male in the land of Egypt, both human and animal. That is why we sacrifice every first-born male animal to the Lord, but buy back our first-born sons.
16 This observance will be a reminder, like something tied on our hands or on our foreheads; it will remind us that the Lord brought us out of Egypt by his great power.' "
17 When the king of Egypt let the people go, God did not take them by the road that goes up the coast to Philistia, although it was the shortest way. God thought, "I do not want the people to change their minds and return to Egypt when they see that they are going to have to fight."
Scripture taken from the Good News Translation - Second Edition, Copyright 1992 by American Bible Society. Used by Permission.