Sermon: Why does the Trinity Matter?

Text: Acts 2:14-36
Second Reading for Trinity Sunday, Series A
Listen to the sermon here!

Grace to you and peace from God our Father and the Lord Jesus Christ.

There is a saying that goes something like this, “In the beginning God created man, and ever since man has been returning the favour.” There’s something to this. We are tempted to fashion God after ourselves, to have a god to suit our fancy. We are tempted invent a god who will solve all our problems or satisfy all our perceived needs. And this is exactly why many don’t like the Creeds, because they won’t be told what to believe. People want to have a pick-and-choose, do-it-yourself, smörgåsbord kind of god.

But, today is the Sunday of the Holy Trinity. Today we confessed the Athanasian creed. This creed stands in the way of our self-chosen gods and says, “Whoever desires to be saved must confess this catholic faith.” Trinity Sunday is a day to take a big, deep breath and confess the incomprehensible – God as one Divine Essence in three Divine Persons, a Unity in Trinity and a Trinity in Unity. “Neither confusing the Persons nor dividing the Substance.” But it’s sure confusing, isn’t it? But this raises two important questions: what exactly is the Trinity and why does my eternal salvation depend upon confessing it?

I. What is the Trinity?

So, what is this Trinity thing? The Trinity is built on three ideas found in your Bible. First, there is only one God. There are not 5000 gods, and there are not even three gods. There is only one God. Second, the Father, the Son, and the Holy Spirit are not identical. It is not three different roles that one person has. They are different persons. Jesus prays to his Father. He is not praying to himself. They’re not the same person. Jesus promises to send another helper, the Holy Spirit. They are separate persons. It’s simple: the Father is not the Son and the Holy Spirit is neither the Father nor the Son. Third, each of these three persons, the Father, the Son, and the Holy Spirit, are each equally and fully divine. Each person is called God and treated as God. But, does that mean we have three gods? No, go back to that first point. There is only one God. We say he is one in essence, and three in person. “Essence” describes what God is. “Person” describes who God is. One what and three whos.

Are you confused yet? Any god who fits comprehensively inside our heads isn’t big enough to be our God anyway. There is no example or analogy which works to explain the Trinity because God isn’t like anything in the created universe. The Christian faith is built on mystery; paradox: God is Three and He is One – a tri-unity. Jesus is God and man – two natures, yet one Person. The Scriptures are God’s Word and man’s word. As a believer, you are both a sinner and justified at the same time. Paradox. Mystery. But what happens when you deny this truth?

II. Denying the Trinity condemns you.

One of the main ideas in Christianity is that we would never know who God is unless he revealed himself to us. In order to have any sort of relationship with God, we must understand and accept God as he has revealed himself. We have to accept God for who he is. The same idea goes for normal human relationships. The only way I can get to know you is if you share things about yourself with me. I don’t get to change details about who you are just because I may not like certain things, and neither can I mould you to make you the way I want.

God has in fact revealed himself to us. That means that we must accept God as he has revealed himself. In the Creation account in our Old Testament reading we see the Triune God at work. God creates. He does so by means of his Word, that Word is his eternal Son. The Spirit hovers over the waters. Creation is a work of the Trinity. We also see the Trinity revealed in the Baptism of Jesus: The Son is baptized. The Father speaks from heaven. The Spirit descends like a dove. This is how God has revealed himself to us: as Father, Son, and Holy Spirit.

The First Commandment tells us that we must have no other gods besides the Lord. If we don’t believe the Trinity, we break the First Commandment. We are in fact making up our own god to suit our own fancy. Put simply, if we refuse to believe that God is the Trinity then we are rejecting how God has revealed himself, and to reject God for who he is. Those who don’t believe in the Trinity end up inventing their own god, one who is made in their image and likeness. And those who don’t care for how God has revealed himself, who would rather not know this God, will still have to face him as their Judge on the Last Day. You cannot have a saving relationship with Jesus if you don’t accept him for who he is as the incarnate Son of God!

III. The Triune God saves you.

That is why it is vital that we realise it is the Triune God who saves you. Salvation is not our work, but the work of the Father, Son, and Holy Spirit. Our salvation is the plan of God the Father. “Jesus, [was] delivered up according to the definite plan and foreknowledge of God” (Acts 2:23). It is the Father who loved the world. It is the Father who not only loved the world, but demonstrated his love by sending his eternal Son into the world, not to judge or condemn the world but so that His Son would be judged and condemned to save the world. The Father sent the Son.

So, the Father sent the Son. Everything the Father does for our salvation, he does through his Son. Jesus Christ, the Son of God, is the one who suffered and died for the sin of the world. “Let all the house of Israel therefore know assuredly that God has made him both Lord and Christ, this Jesus whom you crucified” (Acts 2:36). It is Jesus who was lifted up on the cross and died for us! We would be lost forever without the cross of Christ. On that cross, Christ Jesus paid for sin, your sins and mine. Our guilt is removed and our sins have been atoned for (Is 6:7). So, “it shall be that whoever calls on the name of the Lord shall be saved” (Acts 2:21).

The Father sent the Son. The Son died and was raised for us. And the Father with the Son send the Holy Spirit to us. “This Jesus God raised up, and of that we all are witnesses. Being therefore exalted at the right hand of God, and having received from the Father the promise of the Holy Spirit, he has poured out this which you see and hear” (Acts 2:32-33). By that Holy Spirit, the Son is revealed to us and his gifts are given to us. The Holy Spirit uses the waters of Holy Baptism to give us new life. Your baptism was the day when your heavenly Father adopted you as his child. The Triune name was placed upon you. “Go therefore and make disciples of all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19). In those baptismal waters, the blood of Jesus, his Son, washed away your sin. The Holy Spirit continues to strengthen your faith, so that you keep on trusting in Jesus your Saviour for all your righteousness, forgiveness, and everlasting life.

This is why the doctrine of the Trinity is so important! If you lose the Trinity then God is not the Father who sent his Son. If you lose the Trinity then Jesus is not Lord. If you lose the Trinity, then Jesus is not the one and only mediator between the God and man. If you lose the Trinity, then there is no Saviour to die the cursed death of the Cross to save humanity. If you lose the Trinity, then there is no Holy Spirit to give us new life in Holy Baptism. Without the Trinity there is no salvation because it is the Triune God who saved you.

The Father sends the Son. The Son dies for you. The Father and the Son send the Holy Spirit to proclaim Christ to you and to deliver to you forgiveness, life, and salvation. That’s the Trinity at work. That’s why the Athanasian Creed says, “Whoever does not believe it faithfully and firmly cannot be saved.”


We do not need to invent our own gods, because the Triune God has revealed himself to us in Scripture. You don’t have to understand the mystery of the undivided Holy Trinity, but you do have to confess it and praise Him, because it is the Triune God who saved you and made you a citizen of heaven. The Father sent the Son. The Son died for you. The Father and the Son sent the Holy Spirit. Blessed be the Holy Trinity and the undivided Unity. Let us give glory to him because he has shown his mercy to us. Amen.

May the peace of God, which passes all understanding, keep your hearts and your minds in Christ Jesus. Amen

Published by revfenn

Canadian. Confessional Lutheran pastor. Loci Communicant. Husband. Dad. Bach enthusiast. Middle-Earthling. Nerdy interests on the whole.

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