Acts 2:37–41 shows the first mass influx of people into the church. Men in Jerusalem for Pentecost from across the Roman Empire and beyond are startled to find 120 Galileans speaking their native languages (Acts 2:1–13). Peter uses passages from Joel and Psalms to support his points on several ideas: that Jesus of Nazareth is the Messiah, the Jews had Him killed, God raised Him from the dead, and His resurrection provides hope of forgiveness for His followers (Acts 2:14–36). The crowd is stunned and reacts in the only logical way possible, asking, ”What shall we do?” (Acts 2:37). Peter explains their need for salvation, and thousands respond.
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“Acts 2:38” Bibleref.com
38 Peter said to them, “Repent, and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of sins, and you will receive the gift of the Holy Spirit.