Introduction:
Peter's Sermon at Pentecost, as recorded in the Book of Acts, chapter 2, marks a pivotal moment in the early Christian Church. Delivered shortly after the descent of the Holy Spirit upon the apostles, this sermon is considered the first public proclamation of the Gospel following Jesus Christ's resurrection and ascension. It serves as a foundational event for the establishment of the Church and the spread of Christianity.

Context:
The sermon takes place during the Jewish festival of Pentecost, also known as the Feast of Weeks, which occurs fifty days after Passover. This festival drew Jews from various regions to Jerusalem, creating a diverse audience. The apostles, filled with the Holy Spirit, began to speak in different tongues, astonishing the crowd and prompting questions about the meaning of these events.

Content of the Sermon:
Peter, standing with the eleven apostles, addresses the crowd to explain the miraculous events they are witnessing. He begins by refuting the accusation that the apostles are drunk, stating, "These men are not drunk, as you suppose. It is only the third hour of the day!" (Acts 2:15).

Peter then cites the prophet Joel, declaring that the outpouring of the Spirit is a fulfillment of prophecy: "In the last days, God says, I will pour out My Spirit on all people" (Acts 2:17). This reference establishes the divine origin of the events and connects them to God's redemptive plan.

Proclamation of Jesus as Messiah:
Central to Peter's sermon is the proclamation of Jesus Christ as the promised Messiah. He recounts Jesus' life, death, and resurrection, emphasizing that Jesus was "a man attested to you by God with miracles, wonders, and signs" (Acts 2:22). Peter asserts that Jesus' crucifixion was part of God's predetermined plan, yet he holds the audience accountable for their role in it.

Peter boldly declares the resurrection of Jesus, citing King David's prophetic words: "You will not abandon my soul to Hades, nor will You let Your Holy One see decay" (Acts 2:27). He argues that David spoke of the Messiah, not himself, as David's tomb was still present, whereas Jesus had risen.

Call to Repentance:
Concluding his sermon, Peter calls the crowd to repentance and baptism in the name of Jesus Christ for the forgiveness of sins, promising that they too will receive the gift of the Holy Spirit. He urges, "Save yourselves from this corrupt generation" (Acts 2:40).

Impact:
Peter's sermon results in a profound response, with about three thousand people accepting his message and being baptized. This event marks the birth of the early Church, as the new believers devoted themselves to the apostles' teaching, fellowship, breaking of bread, and prayer.

Theological Significance:
Peter's Sermon at Pentecost is significant for several reasons. It affirms the fulfillment of Old Testament prophecy, establishes the centrality of Jesus' death and resurrection in God's salvific plan, and highlights the role of the Holy Spirit in empowering the Church. The sermon underscores the call to repentance and faith in Jesus Christ as the means of salvation, setting the stage for the spread of the Gospel to all nations.