When the people heard this, they were cut to the heart and said . . . “What shall we do?” — Acts 2:37
As Peter stands before the crowd, the Holy Spirit guides his words. Jesus promised this guidance when he said, “I will give you words and wisdom that none of your adversaries will be able to resist or contradict” (Luke 21:15), and, “When he, the Spirit of truth, comes, he will guide you into all the truth . . . and he will tell you what is yet to come” (John 16:13).
Peter’s message is therefore rooted in the promises of God and the fulfillment of those promises in Christ. He recalls the words of the prophet Joel, which contain not only the promise of God’s Spirit poured out on all people, but also an invitation to call on the name of the Lord and be saved.
Who is this Lord? It is Jesus, whom the people crucified.
By weaving back and forth from the promises of God and the life of Jesus, Peter builds his case to this key point: “God has made this Jesus, whom you crucified, both Lord and Messiah.” And the people ask, “What shall we do?”
Peter then guides these listeners to “repent and be baptized . . . in the name of Jesus Christ.” And they receive the gift of the Holy Spirit. Pressing further, he urges and pleads with others to call on the Lord’s name. And about 3,000 people believe and are baptized!