Exodus 13:15

15 yea, it cometh to pass, when Pharaoh hath been pained to send us away, that Jehovah doth slay every first-born in the land of Egypt, from the first-born of man even unto the first-born of beast; therefore I am sacrificing to Jehovah all opening a womb who [are] males, and every first-born of my sons I ransom;

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 `And every firstling of an ass thou dost ransom with a lamb, and if thou dost not ransom [it], then thou hast beheaded it: and every first-born of man among thy sons thou dost ransom.
14 `And it hath been, when thy son asketh thee hereafter, saying, What [is] this? that thou hast said unto him, By strength of hand hath Jehovah brought us out from Egypt, from a house of servants;
15 yea, it cometh to pass, when Pharaoh hath been pained to send us away, that Jehovah doth slay every first-born in the land of Egypt, from the first-born of man even unto the first-born of beast; therefore I am sacrificing to Jehovah all opening a womb who [are] males, and every first-born of my sons I ransom;
16 and it hath been for a token on thy hand, and for frontlets between thine eyes, for by strength of hand hath Jehovah brought us out of Egypt.'
17 And it cometh to pass in Pharaoh's sending the people away, that God hath not led them the way of the land of the Philistines, for it [is] near; for God said, `Lest the people repent in their seeing war, and have turned back towards Egypt;'
Young's Literal Translation is in the public domain.