We can resolve much of the confusion in Peter’s first sermon by understanding the JEWISH background. Acts 2 is addressing law observant Jews that are gathered together to observe the Jewish Feast of Pentecost (verse 1). There are no Gentiles (non - Jews) present; Peter addressing them says, v: 22 “Men of Israel,” v: 36 “Therefore let all the house of Israel know.” Acts 2:37 Now when they heard this, they were cut to the heart, and said to Peter and the rest of the apostles, “Men and brethren, what shall we do?” He is addressing Jews, as a NATION, not individuals. The NATION of Israel was under divine judgment for rejecting Jesus. They were instructed to repent and be baptized. They were to repent of the view they held of Jesus, to remove themselves from the accursed generation that rejected him. If you realize who He is, change your mind and show it is changed by being baptized. Acts 2 presents a group of people who come to realize that they are guilty and are asking what THEY must do. He is telling them to repent, change their mind about Jesus: Turn toward Him instead of rejecting him. Believe in him as God’s Son, the Messiah sent of God, and not a blasphemer. In Acts 2:40, he concludes by admonishing them, “be saved from this perverse generation.” This is the same generation that Jesus called wicked pronouncing that they had committed the unpardonable sin in Mt. 12:22-45. The public declaration of being baptized in Jesus’ name meant they would publicly show their repentance and that He is their Messiah through the act of baptism. The Jews that believed showed their repentance by responding and being baptized in the name of the Person they had rejected as their Messiah. It was an illustration and identification of their new allegiance to Jesus. Their acceptance of Jesus (response) signified by their public baptism, brought these individuals out from under the divine judgment on the generation that rejected Christ, (blasphemed the Holy Spirit) that would later conclude with the downfall of Jerusalem, ending in 70 AD. 

Peter stating “let every one of you be baptized,” the word “you” (singular) in the command to “be baptized.” The last part of Acts 2:38, “and you shall receive,” is addressed to the whole crowd listening to Peter (a second person plural is used) – the point of this grammar is that “the gift of the Holy Spirit” is connected to the individual’s repentance, not their water baptism. The command to “be baptized” is addressed to those individuals who already repented and were forgiven. We find baptism always comes after one believes.

Peter is NOT teaching that no one could be saved until they were baptized. We have too many clear examples that teach otherwise. Peter says later in Acts 3:19: “Repent, then, and turn to God, so that your sins may be wiped out, that times of refreshing may come from the Lord,” eliminating any baptism. Both are by the same author, as is Acts 10:43; which explains they were saved - by faith without baptism. Acts 10:43-48 Peter preaches to the Gentiles for the first time. In v. 43 it says “... whosoever believeth in him shall receive remission of sins.” through His name, is forgiveness of sins. The same Peter spoke both.