Peter said to them, “Repent, and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit.”
Why did Peter add the condition of baptism, presumably water baptism, for the forgiveness of sin, when he elsewhere stated: “Therefore repent and return, so that your sins may be wiped away, in order that times of refreshing may come from the presence of the Lord.” (Acts 3:19) Peter is identifying a specific problem that the Jews had.
John 7:13: “Yet no one was speaking openly of Him for fear of the Jews.”
John 9:22: “His parents said this because they were afraid of the Jews; for the Jews had already agreed that if anyone confessed Him to be Christ, he was to be put out of the synagogue.”
John 12:42: “Nevertheless many even of the rulers believed in Him, but because of the Pharisees they were not confessing Him, for fear that they would be put out of the synagogue.”
These many were in the secret service, that is, secretly believing in Jesus.
In terms of ex-communication, why do people remain in churches that they ought not belong to? Perhaps it is due to the confidence in and the approval of man. Yet, Jesus stated: “He who loves father or mother more than Me is not worthy of Me; and he who loves son or daughter more than Me is not worthy of Me. And he who does not take his cross and follow after Me is not worthy of Me. He who has found his life will lose it, and he who has lost his life for My sake will find it.” (Matthew 10:37-39)
Perhaps this situation in Israel is why Jesus stated: “He who has believed and has been baptized shall be saved; but he who has disbelieved shall be condemned.” (Mark 16:16) So there really was a fear-problem in Israel, of many secretly claiming to believe in Jesus, though publicly denying Him for fear of ex-communication. They refused to publicly confess Christ before men because they feared men more than they feared God. They trusted more in their right-standing with the local synagogue, than in their right-standing with the miracle-working Messiah. They didn’t truly believe in Him. However, those who were publicly baptized, also ended up publicly professing Christ, and much more. Acts 2:41-47 records: “So then, those who had received his word were baptized; and that day there were added about three thousand souls. They were continually devoting themselves to the apostles' teaching and to fellowship, to the breaking of bread and to prayer. Everyone kept feeling a sense of awe; and many wonders and signs were taking place through the apostles. And all those who had believed were together and had all things in common; and they began selling their property and possessions and were sharing them with all, as anyone might have need. Day by day continuing with one mind in the temple, and breaking bread from house to house, they were taking their meals together with gladness and sincerity of heart, praising God and having favor with all the people. And the Lord was adding to their number day by day those who were being saved.”
Those of Acts 2:37 needed to become publicly baptized, and shake loose their confidence in the synagogue, and trust solely in Jesus for salvation. Previously, they didn’t trust in Christ alone, but now after taking the plunge in believer’s baptism, they submitted themselves into the care of the Lord.
A Pastor tells of an account in which a woman had attended a revival Camp Meeting, and at the conclusion, was ready to submit her life to the Lord, but she was afraid to come forward and give a public profession. So she asked a Deacon if she could be saved from the back. The Deacon answered, “No.” (Already the analogy seems off, as that statement would make for errant theology, but wait, there’s more.) The next day of the Camp Meeting, the woman again falls under conviction and is ready to submit her life to the Lord, when she asks the Deacon, “Can’t I be saved back here!” “No,” the Deacon again replies. So in the final night of the Camp Meeting, the woman, completely exasperated, gives in a says, “Ok, I will do anything to get over this feeling of conviction and self-condemnation. I will go forward if I must.” That’s when the Deacon replied, “Ok, now you can be saved from back here.” In this instance, the Deacon was not making a broad sweeping theological statement, but simply addressing a specific problem area that was hindering her from truly experiencing the Kingdom of God. Similarly, in the apostle Peter’s reply, he was highlighting a specific problem area that was hindering the Jews from truly experiencing the Kingdom of God.
In the case of Acts 2:38, the Jews needed to do more than just make a profession. They needed to experience the Kingdom of God by stepping out and following through. It’s not that Baptism is a saving act which confers forgiveness, no more than giving up all of one’s possessions confers eternal life, or sacrificing one’s eldest male son confers eternal life. In all of these examples, specific hindrances are being addressed.
In the case of the Jews, they had been unwilling to openly profess Christ, by being publicly baptized, since they didn’t truly believe in Him, and therefore, their sins remained according to the Lord’s warning at Matthew 10:33. In witnessing to someone, and quoting John 3:16, has anyone ever put you off by saying, “Okay, so I believe,” and yet by their actions, they clearly indicate that they do not believe, and are by no means sincere in submitting their life to the Lord? The reason is that there’s a difference between believing in your head and believing in your heart. Just because a person tells you that they believe, does not necessarily mean that they truly believe in their heart. So if anyone puts you off, in a similar manner, tell them, “Okay, then since you believe, are you ready to be baptized?” The apostle Peter had essentially challenged the Jews to follow through.
John Calvin comments: “Because we receive Christ’s gifts by faith, and baptism confirms and increases our faith, forgiveness of sins, which is the result of faith, is linked to it, as a superior to an inferior. In addition to this we must not derive our doctrine of baptism from here, as Peter is just touching on it at this point. Our old nature is crucified, as Paul teaches, so that we may live a new life (Romans 6:4, 6). Scripture teaches everywhere that baptism is a sign and token of repentance. In this passage in Acts Peter is not teaching about baptism but the forgiveness of sins. He says incidentally that baptism is the confirmation of the forgiveness of sins.” (Acts: Calvin, The Crossway Classic Commentaries, p.45, emphasis mine)
Baptism may confirm it, but it does not confer it, so yes, “baptism confirms and increases our faith.” Faith and repentance are matters of the heart, whereas baptism is an outward expression of an inward change. God looks at the heart, and that’s why Paul stated: “If you confess with your mouth Jesus as Lord (outward profession), and believe in your heart (inward confession) that God raised Him from the dead, you will be saved; for with the heart a person believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation.” (Romans 10:9-10) Jesus stated: “Truly, truly, I say to you, he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life.” (John 5:24) Jesus first mentioned “hears My word” because faith comes from hearing the word of Christ, just as Paul indicated at Romans 10:17. Jesus stated: “Truly, truly, I say to you, he who believes has eternal life.” (John 6:47)