The Westminster Confession of Faith says “Not only those that do actually profess faith in and obedience unto Christ, but also the infants of one, or both, believing parents, are to be baptized… it be a great sin to contemn or neglect this ordinance, (Luk 7:30; Exd 4:24-26)” (28.4-5)
Note the appeal to Exodus 4:24-26
24 At a lodging place on the way, the Lord met Moses and was about to kill him. 25 But Zipporah took a flint knife, cut off her son’s foreskin and touched Moses’ feet with it. “Surely you are a bridegroom of blood to me,” she said. 26 So the Lord let him alone. (At that time she said “bridegroom of blood,” referring to circumcision.)
NIV
Many find this passage bizarre and don’t know what to make of it, but it’s not terribly confusing.
The two instances of “Moses” are not actually in the Hebrew. They are interpretation provided by the translators. The Hebrew simply says “met him” and “touched his feet” (see ESV, NKJV, CSB). But who else could “him” refer to? “The Hebrew is slightly ambiguous… it may be against Moses’s firstborn, Gershom” (Reformation Study Bible; T.D. Alexander). The immediately preceding verses read
22 Then you shall say to Pharaoh, ‘Thus says the Lord, Israel is my firstborn son, 23 and I say to you, “Let my son go that he may serve me.” If you refuse to let him go, behold, I will kill your firstborn son.’”
Whether one follows the MT Hebrew of v. 24 (“Yahweh met up with him and sought to kill him”) or the likely original lxx/Tg. of v. 24 (“The Angel of the Lord met up with him and sought to kill him”), the same essential point is made: God was not going to allow someone (Gershom—not Moses: the text of 4:24–26 never mentions Moses!) to get to Egypt alive without a decisive change in their circumcision status. The fact that this story follows immediately the warning of Yahweh about the potential death of Pharaoh’s firstborn son provides a spatial setting in the text: we now read a story about the potential death of Moses’ firstborn son, upon whose fate the focus of the pericope should naturally fall…
The Hb. grammar of the passage uses proleptic pronouns to refer to Gershom at first and never names Moses at all. Gershom is referred to in v. 25 finally as her son, which tells the reader who it was that God threatened to kill. The choice of the NIV to include the name of Moses twice (in brackets each time) is just that: a translator’s choice, not a matter of literal translation. Its effect is to skew the reader’s attention to Moses rather than the actual referent of the pronouns, her son.
Stuart, Volume 2
There is every reason to believe… that the author is speaking of Gershom, the first-born son of Moses… It is likely that Moses is not the central figure of this episode, but rather his son (cf. Gen. 17:14).
Currid
After issuing the threat of killing Pharoah’s firstborn son for disobeying God, God was going to “cut off” Moses’ son for not being circumcised, as He said He would. “Any uncircumcised male who is not circumcised in the flesh of his foreskin shall be cut off from his people; he has broken my covenant” (Genesis 17:14). This was hardly the Covenant of Grace.
[C]ircumcision symbolized the oath-curse by which the Abrahamic community confessed themselves under the judicial authority and more precisely under the sword of God Almighty… The oath whose curse sanction circumcision symbolized was an oath of allegiance. It was an avowal of Yahweh as covenant Lord, a commitment in loyalty to him.
Kline, By Oath Consigned, 41
If circumcision is replaced by baptism, such that all the children of believers must be baptized or be “cut off” then all the children of baptists should be dead. Thankfully, baptism is not a replacement of circumcision.
Further Reading
A Bridegroom of Blood
The Strangest Circumcision Story Ever Paul Carter
THE BLOODY BRIDEGROOM AND THE BLOODY LAMB: AN EXEGESIS OF EXODUS 4:19-26 Nathaniel Vroom