Do the redemption laws only apply to firstborn sons?

Answer:

"Consecrate to Me all the firstborn, whatever opens the womb among the children of Israel, both of man and beast; it is Mine" (Exodus 13:2).

"And it shall be, when the LORD brings you into the land of the Canaanites, as He swore to you and your fathers, and gives it to you, that you shall set apart to the LORD all that open the womb, that is, every firstborn that comes from an animal which you have; the males shall be the LORD'S. But every firstborn of a donkey you shall redeem with a lamb; and if you will not redeem it, then you shall break its neck. And all the firstborn of man among your sons you shall redeem. So it shall be, when your son asks you in time to come, saying, 'What is this?' that you shall say to him, 'By strength of hand the LORD brought us out of Egypt, out of the house of bondage. And it came to pass, when Pharaoh was stubborn about letting us go, that the LORD killed all the firstborn in the land of Egypt, both the firstborn of man and the firstborn of beast. Therefore I sacrifice to the LORD all males that open the womb, but all the firstborn of my sons I redeem'" (Exodus 13:11-15).

"You shall not delay to offer the first of your ripe produce and your juices. The firstborn of your sons you shall give to Me" (Exodus 22:29).

"All that open the womb are Mine, and every male firstborn among your livestock, whether ox or sheep. But the firstborn of a donkey you shall redeem with a lamb. And if you will not redeem him, then you shall break his neck. All the firstborn of your sons you shall redeem. And none shall appear before Me empty-handed" (Exodus 34:19-20).

"Now behold, I Myself have taken the Levites from among the children of Israel instead of every firstborn who opens the womb among the children of Israel. Therefore the Levites shall be Mine, because all the firstborn are Mine. On the day that I struck all the firstborn in the land of Egypt, I sanctified to Myself all the firstborn in Israel, both man and beast. They shall be Mine: I am the LORD" (Numbers 3:12-13).

"And for the redemption of the two hundred and seventy-three of the firstborn of the children of Israel, who are more than the number of the Levites, you shall take five shekels for each one individually; you shall take them in the currency of the shekel of the sanctuary, the shekel of twenty gerahs" (Numbers 3:46-47).

"After that the Levites shall go in to service the tabernacle of meeting. So you shall cleanse them and offer them, like a wave offering. For they are wholly given to Me from among the children of Israel; I have taken them for Myself instead of all who open the womb, the firstborn of all the children of Israel. For all the firstborn among the children of Israel are Mine, both man and beast; on the day that I struck all the firstborn in the land of Egypt I sanctified them to Myself. I have taken the Levites instead of all the firstborn of the children of Israel" (Numbers 8:15-18).

"Everything that first opens the womb of all flesh, which they bring to the LORD, whether man or beast, shall be yours; nevertheless the firstborn of man you shall surely redeem, and the firstborn of unclean animals you shall redeem. And those redeemed of the devoted things you shall redeem when one month old, according to your valuation, for five shekels of silver, according to the shekel of the sanctuary, which is twenty gerahs" (Numbers 18:15).

"Now when the days of her purification according to the law of Moses were completed, they brought Him to Jerusalem to present Him to the Lord (as it is written in the law of the Lord, "Every male who opens the womb shall be called holy to the LORD"), and to offer a sacrifice according to what is said in the law of the Lord, "A pair of turtledoves or two young pigeons"" (Luke 2:22-24).

I tried to list out every statement dealing with firstborn children in Israel. All firstborn children are dedicated to God and firstborn males were originally selected to be the priests in Israel. This was replaced by the tribe of Levite, but all firstborn males had to be redeemed by a payment of five shekels to the Temple. Firstborn females were considered as belonging to God but did not have to be redeemed because they were not selected for service to God. Thus, a family that has a girl first and then a boy would not have to pay the five shekels because the rules apply to the child who opens the womb. If the first child a woman has is a boy, then there is a redemption fee.

Some commentators look at this as only applying to the first son born into a family, regardless of how many daughters preceded him. I have to disagree since the laws talk about "the first to open the womb."

My point is that a firstborn child could not be vowed with the expectation of redeeming the child because the child already was claimed by God. Firstborn sons were claimed for service and could be bought back with five shekels. But they could not be bought back a second time as a result of a vow. Since there is no provision for buying back a firstborn daughter and because she already belongs to God, if a daughter is vowed, there is no way to redeem her back from God.