“Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are His judgments and how inscrutable His ways…from Him and through Him and to Him are all things. To Him be glory forever. Amen.” St. Paul wrote this to the Romans after considering the mystery of salvation. God the Father sent forth His only-begotten Son into the flesh to suffer and die for the sins of the world. By this work, He accomplished salvation for His people. Those who are saved, He foreknew and elected to salvation by granting them the gift of faith – which itself is worked in human hearts through the Holy Spirit. This great grace and love of God is hard for us humans to understand, so St. Paul simply ends with a doxology – a hymn of praise to the Father, Son, and Holy Spirit.
Today we celebrate the Festival of the Holy Trinity. This is a Sunday set aside for centuries to give praise to our glorious and awesome God by speaking specifically about this wonderful doctrine. The Christian faith is wrapped up into this doctrine: we worship one God who exists eternally in three persons. None is before or after another, none is greater or lesser than the other. Yet, there are not three Gods, but one God. Though human reason cannot understand, yet faith confesses that God has revealed Himself to us as a Trinity. Our salvation rests in Him alone.
In our time together today, we want to confess both what we believe about the Trinity and why this doctrine is important. We’re going to do it backwards, though, and start with why faith in the Trinity is important. We’ve been spending a lot of time in the Easter season and Pentecost hearing from Jesus’ final words before His passion. Shortly before He was betrayed, in St. John’s Gospel there’s what is called the “High Priestly Prayer.” Right at the start of the prayer, our Lord prayed this, “Father, the hour has come; glorify Your Son that the Son may glorify You, since You have given Him authority over all flesh, to give eternal life to all whom You have given Him. And this is eternal life, that they know You, the only true God, and Jesus Christ whom You have sent.” Jesus breaks down for us what eternal life is. In addition to rescue from sin and death and living in eternal joy, eternal life is to know God and to be in fellowship with Him. To be in communion with God is to receive eternal life. Apart from knowledge of God, there is no life.
Therefore, God revealed Himself to mankind. He revealed Himself generally through nature and the conscience. But, so that man might know Him fully and thus receive salvation, God revealed Himself through the Scriptures. Through the Scriptures He has revealed Himself to be a plurality of persons, yet unity of substance. Trinity is the word we use to describe this. Trinity means, “three-in-one.” The Trinity is revealed to us throughout Scripture, but there are two passages which you probably already know. The first, “Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.” The second is from St. Paul, “The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.” Our Lord tells us to Baptize in the name of the Triune God, yet is also clear to confess that He and the Father are one God. You might’ve noticed last week in the Tower of Babel, how the one God spoke in the plural, as He also did at Creation.
The first question to answer today is why we believe in the Trinity, and why are compelled to confess our faith. The answer to that is because to know God is to know eternal life. To not know Him is death. So that we might have life, the Lord revealed Himself to us in Scripture as one God in three persons. Scripture teaches us that we are saved by faith. But, faith saves not because it is a good work which merits righteousness. Faith saves because of its object. We are saved not because we have faith, but because of what our faith is in – namely, in God the Father who sent His Son and, who by the Holy Spirit has called us to faith.
Since we’re doing this backwards, the next question is what do we believe? We believe, as we’ve already said, “the catholic faith is this, that we worship one God in Trinity and Trinity in Unity, neither confusing the persons nor dividing the substance…the Father is God, the Son is God, the Holy Spirit is God; and yet there are not three God, but one God.” This is the Christian faith. We believe in one eternal God, who exists in three persons. All three are God, all three are Lord. None are before or after another, none is lesser or greater than another. They differ in relation to each other in that the Father begat the Son, the Son is begotten of the Father, and the Spirit proceeds from the Father and the Son. They differ in their work in that the Father primarily is the Creator, the Son the Redeemer, and the Spirit the Sanctifier. Yet, they are all active in each work as one God. You’re probably thinking that this is impossible for us to understand, and you’re right. Human reason cannot understand the Trinity. It can only and must be believed.
We believe in one God, three persons: Father, Son, and Holy Spirit. None are more God than the other, and none are less. There are some common misunderstandings when it comes to the Trinity. The first is what non-Christians sometimes charge us with, namely, that we are really polytheists – that we worship three gods. That is not true. We hold to the Scripture which says, “Hear, O Israel: The Lord our God, the Lord is one.”
On the other side are misunderstandings that were created within the Church, which the Nicene and Athanasian Creeds were written against. In order to preserve the oneness of God, some taught that the Son was, indeed, God – but was created by the Father. They said that there was a time when the Son did not exist. Others, taught that the three persons of the Trinity were just different masks that the one God put on. In other words, you could not have all persons of the Trinity in the same place at the same time. And still, others, which are today known as Unitarians, taught that the one God acts in three different ways, sometimes as the Father, sometimes as the Son, and sometimes as the Spirit.
Against these teachings we believe the Scripture, such as at our Lord’s Baptism. Our Lord was in the water, the Father spoke from heaven, and the Spirit descended in the form of a dove. We believe the words of our Lord, who taught us to baptize in the one name of the Father, Son, and Holy Spirit. And, we receive the words of angelic praise, “Holy, holy, holy is the Lord of hosts; the whole earth is full of His glory.” We worship the God of our salvation, who has and always will exist in three persons, Father, Son, and Holy Spirit.
As we’re nearing the close of this sermon, since we’ve answered why we should confess the Trinity and what we believe, we might ask, also, what comfort this doctrine brings. I would venture that the comfort that this doctrine brings is this: we have divinely transcendent God who far above all creation, whose ways are unsearchable, unknowable, and inscrutable – but who yet is also near and ever present in our lives and at work for our salvation. God the Father is the author and source of all life, He created all things and knit us together in our mothers’ wombs. He provides for us our daily bread and protects us from all evil. He sent forth His Son.
The second person of the Trinity became man. He did not change from God to man but brought humanity up into Himself. He suffered and died for the sins of the world. By His ascension, He is preparing our own ascension to His side and He continues to dwell among us by His Word and Sacrament. From Him and the Father, the Spirit proceeds. The Spirit works through the Word of the Son to call all people to faith. He creates faith in the hearts of those who hear the Word and works through the Sacraments to sustain them. The Spirit dwells even within our hearts and intercedes for us with the Son to the Father. He comforts us in our weaknesses and helps us to pray.
The doctrine of the Trinity is not something we’ll understand this side of eternity, but it is true, and our salvation depends on it. Jesus said eternal life is knowing God and knowing Him as He has been revealed by the Son through the Holy Spirit. We who have received that life, therefore, give all glory to the Triune God: Father, Son, and Holy Spirit. “Blessed be the Holy Trinity and undivided Unity. Let us give glory to Him because He has shown His mercy to us.”
 Romans 11:33, 36, English Standard Version.
 Jn. 17:1-3.
 Mt. 28:19.
 2 Cor. 13:14.
 Athanasian Creed, 3-4; 15-16.
 Deut. 6:4.
 Is. 6:3.