Acts 2:37-38

Now when they heard this, they were cut to the heart [with remorse and anxiety], and they said to Peter and the rest of the apostles, “Brothers, what are we to do?” And Peter said to them, “Repent [change your old way of thinking, turn from your sinful ways, accept and follow Jesus as the Messiah] and be baptized, each of you, in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit.