You may notice that the sermon text this morning is mysteriously missing a verse (if you’re reading the ESV). In some copies of the book of Acts, a conscientious scribe added the following line, after the Ethiopian says to Philip, “What prevents me from being baptized?" (Act 8:36 ESV): “And Philip said, ‘If you believe with all your heart, you may.’ And he answered and said, ‘I believe that Jesus Christ is the Son of God’” (Act 8:37 NASB).
Why would a scribe add something like this? Maybe it caused a scribe or two heartburn that Luke did not record an explicit profession of faith on the lips of the Ethiopian eunuch. Maybe a scribe or two thought it best to make it abundantly clear that the Ethiopian knew what he was doing. After all, there is a link between a profession of faith and baptism. In fact, the book of Acts is full of examples of men and women making professions of faith and getting baptized. To reinforce this connection, a scribe or two amplified what Luke wrote, and that amplification made its way in some copies of Acts.
Whatever the real reason for this missing verse, the general connection between a profession of faith and baptism is obvious both in Acts 8 and earlier chapters. And yet, that connection does not define the recipients of baptism. After all, whole households will be baptized in the book of Acts, and that has contributed to the differences within the church over the proper recipients of baptism.
But Robert Letham offers a concise statement regarding the recipients of baptism that I think helps to clarify things. He says that “baptism is to be administered when a person can be called Christian.”
Outwardly speaking, the name of Christian cannot be applied to an adult believer until that person has repented of his sins and believed on the Lord Jesus. But when someone has professed faith in Christ, has committed to follow Christ, then that person can be called a Christian and that person ought to be baptized without delay and without qualification. Hence, the Ethiopian eunuch was baptized on the spot.
But what about Simon the magician? Last week, we saw that Simon the magician, who had previously enthralled the people of Samaria with his magic or trickery, was himself enthralled by the word and work of Philip as Philip proclaimed the Christ. And in response to the gospel, “even Simon himself believed,” Luke tells us, and even Simon was baptized (Acts 8:13).
But things quickly soured for Simon. Very shortly after being baptized, Simon demonstrates his acute lack of understanding of the Lord Jesus when he offered money in exchange for the gift of giving the Holy Spirit. As we talked about last week, since the gifts are inextricably bound up with the giver, Simon’s offer commoditized Jesus. Simon devalued the Lord Jesus from the most sympathetic, able, and willing savior to a financial transaction. And he did this all after believing and being baptized without delay or qualification.
For the reason, Letham says, “The apostles made no delay in baptizing, even at the risk that a person might fall away from the faith afterward. The tragic possibility of apostasy always exists; the most meticulous teaching or the presence of the apostles was not of itself sufficient to prevent it.” In this way, no absolute or infallible judgment is ever made in the baptism of those who can be called Christians.
And that is helpful for us in understanding why we baptize our babies. Though profession of faith is closely connected to being called a Christian, it is by no means the only way to be called a Christian, or to be connected to the covenant community. After all, “Corporate solidarity is an essential feature of biblical revelation.” This is why Paul can say that the children of a believing parent, regardless of the state of the other parent, are holy (1 Cor 7:14).
All of this means that the church administers baptism with a judgment of charity in the case of an adult who publicly professes faith and of a child who is born into a believing family. Both can be called Christians; neither is guaranteed to bear fruit in keeping with repentance. Both will endeavor to improve their baptisms; neither can boast in “earning” their baptism.
Therefore, all who are called Christians, both adults and children, ought to be baptized, and all who are baptized ought to give thanks to God for the gift of salvation.
 Robert Letham, Systematic Theology (Wheaton: Crossway, 2019), 718.  Letham, Systematic Theology, 718.  Letham, Systematic Theology, 721.