Christians have held a festival in honor of the Holy Trinity since the 800’s, when it was celebrated in French monastic communities. In the fourteenth century, the festival was added to the Church Calendar and has been celebrated throughout the world since that time.

Every celebration of Baptism and Communion is a trinitarian celebration, just as every gathering, “In the Name of the Father, the Son, and the Holy Spirit,” is done in union with the Blessed Trinity.

In the power of the Holy Spirit, the Church gathers on Sunday—the day of the resurrection—to offer thanksgiving to the Father for Christ’s saving life and the endowment of the Holy Spirit, ever present in the gifts of the Word and Sacraments. Preachers will employ the familiar verbiage of the Invocation, baptismal “formula,” Athanasian Creed, the Eucharistic prayer, and Benediction within their sermon to acclimate their auditors to the trinitarian content of our faith.

Acts 2:14a, 22-36 seems like a curious text for Trinity Sunday. Might it be out of place as a Scripture revelation of the Father, Son, and Holy Spirit? Not at all. The Apostle Peter’s monumental sermon on Pentecost declares the Kingdom purposes and divine saving work of the Father, Son, and Holy Spirit which culminates in the new world order with Christ in charge, governing in the power of the Spirit. And where might the point of contact be with his auditors on Pentecost (and every time this good news is proclaimed)? Peter answers: Believe the Gospel and receive Baptism (2:38-39).

There could not be a better day for remembering Baptism than the Festival of the Holy Trinity. It is the direction toward which Peter’s sermon terminates (that is, from God’s Word proclaimed to God’s Word in sacramental action). How are persons baptized? “Into the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19).

There could not be a better day for remembering Baptism than the Festival of the Holy Trinity.

Peter’s employment of the Psalms and Prophets specifies that the God which he proclaims as having acted through “this Jesus” is precisely the God of Israel (2:22-23). The author of Hebrews says as much in his opening line: “Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these last days He has spoken to us by His Son” (1:1-2). The God of creation, the God of history, the living God finds consummate revelation in the person, word, and works of Jesus, “...delivered up according to the definite plan and foreknowledge of God” (Acts 2:23).

This is the God who was proclaimed in Peter’s sermon at Pentecost. The sermon itself was both short and extraordinary. It proclaimed Jesus as the Christ of God to people who did not know Him as such. But they did know about King David. So, Peter’s sermon proclaimed Jesus as both David’s son and David’s Lord. As David represented ancient Israel, even more so Jesus represents His reconstituted Israel of both Jews and Gentiles as the world’s rightful King. The David, the Psalms, and the prophets declare Jesus, attested, “...by mighty works and wonders and signs” (2:22), to be, “exalted at the right hand of God” (2:33), and “to be both Lord and Christ” (2:36). Jesus is King. He is in charge. It is the Gospel, sweet gospel. But this sermon also says, and it says in no uncertain terms, “You crucified Him.” It is the Law, stinging law. Notwithstanding, rejoice! This Jesus, even in His post-resurrection state, abides as the ever-crucified Lord (compare this to how Matthew 28:5 notes in the present tense: “You seek Jesus who is crucified.”). Fear not, but instead resort to the crucified Son who exhibits the Father’s loving forgiveness and bestows the Holy Spirit.

Here, the preacher has options either to work through the prophetic content of Peter’s sermon to underscore fulfillment or fast-forward to the end of the sermon. If the preacher jumps to the end, he will see how people reacted to the news that there was, at the right and of God, His only Son, both Lord and Christ, and they had, in fact, crucified Him. Both lead to open declarations of the Law of God and so, the question posed to Peter and the rest of the Apostles: “Brothers, what shall we do?”

If the men of Jerusalem had asked their question of anyone else, the answers would all have this in common: They would tell you to look within yourself and to make your very best effort to be the best you can to fulfill various standards of law, some more severe, some less.

Fear not, but instead resort to the crucified Son who exhibits the Father’s loving forgiveness and bestows the Holy Spirit.

Peter says, “Repent.” Repent of it all and, “...be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins” (2:38). His sermon had accomplished the first part. Confronted with the truth of God, his auditors were drawn to repentance. We read how, “They were cut to the heart.” They did not do this themselves. They did not reach the conclusion by themselves, but the Word of God, the Law of God, worked within them by the Holy Spirit, accusing them, condemning them, and bringing them to repentance. The Law is the Trinity at work.

But that is no cure. To know the problem is not to solve it. So, Peter went on, “Be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins.” This declaration is established by the content of the pericope for Trinity Sunday, Acts 2:22-36. Peter then declares good news, not good advice. The crucifixion, necessitated by our sins that condemn us, now resounds as the victory of Christ over sin and death, capped by the dawning of the new creation in Jesus’ resurrection! Believe. Be baptized. The action here is entirely from God towards us. This is what sets it apart from every religion and philosophy as the Gospel — good news, as opposed to confected, religious obligation.

Just as the condemnation embraces us even now, so too does the remedy and the promise — both are found in the cross of Christ. "You crucified Christ,” Peter said. But that was not the end of it: “This Jesus, delivered up according to the definite plan and foreknowledge of God, you crucified and killed by the hands of lawless men. God raised Him up, loosing the pangs of death, because it was not possible for Him to be held by it” (2:23-24). “Your sin,” the preacher declares, “could not consign Jesus to eternal death. And it will not consign you to eternal death either. For Christ has been raised as the first fruits of those who believe.” Glory be to the Father, Son, and Holy Spirit on this Holy Trinity Sunday for the great work of redemption accomplished through the history of Israel and reaching its climax in our Lord Jesus Christ!

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Additional Resources:

Concordia Theology-Various helps from Concordia Seminary in St. Louis, MO to assist you in Acts 2:14a; 22-36

Text Week-A treasury of resources from various traditions to help you preach Acts 2:14a; 22-36.