Grace, mercy and peace be unto you from God, our Father, and from our Lord and Savior Jesus Christ. Amen.

St. Augustine once said that anyone who denies the Trinity is in danger of losing his salvation, but anyone who tries to understand the Trinity is in danger of losing his mind. In the Athanasian Creed we affirm that denying the Trinity leads to damnation, but in confessing that same Creed perhaps we have felt like our minds were being blown away, if not lost, by its deep truths. That is why the Creeds are confessions of faith in the Triune God as He has revealed Himself to us, not explanations of how God is who He is.

Holy Trinity Sunday is about marveling at the great mercy the Trinity has had on us by creating, redeeming, and sanctifying us. We aren't here to examine the Trinity as a logical puzzle or mathematical problem. That approach would put us in the driver's seat, at point number one, with the Triune God at point number two. Orthodox theology works in the opposite direction, from God to us. He didn't have to create, redeem, and sanctify us. He gives, and we are given to. He reveals to us everything we need to know of Him and His works, and these gifts should be received with gratitude by us.

The greatest gift God the Father has given us is His Son, as John 3:16 so clearly proclaims: "God loved the world this way: He gave His only-begotten Son so whoever believes in Him will not perish but will have everlasting life." So on Holy Trinity Sunday, everything is still all about Jesus, especially about the startling confession, "Jesus Christ is Lord." Or as St. Thomas said to Jesus on the Sunday after Easter: "My Lord and My God." We Christians worship Jesus as the Lord God Himself, because we believe He is!

But for Jesus to be God means that God has to be the Trinity. In the Old Testament, the Lord, Yahweh, revealed Himself to Israel as the one true God: "Hear O Israel, the Lord our God, the Lord is one!" That was the basic creed He gave them to confess. But then the man Jesus of Nazareth came along calling Himself the Son of God, speaking and acting as if He were the Lord God Himself. This did not fit in with most Jews' way of understanding God as one, so they rejected Him.

In John 5, Jesus heals a man who had been an invalid for 38 years. The Jews took issue with this because it was the Sabbath, the day of rest, and Jesus was working at healing. So Jesus answered, "My Father is working until now, and I am working." He was calling Himself, along with the Father, the Lord of the Sabbath, the One who had given Israel the day of rest to begin with. Then St. John explains, "This was why the Jews were seeking all the more to kill him, because not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God" (John 5:16-18). To be equal with God is to be God, and for a man to present Himself in such a way was scandalous to the Jews. In fact, if Jesus had not been telling the truth about His divinity, it would have been blasphemy, and the Old Testament penalty for blasphemy was death by stoning, and that's what the unbelieving Jews sought to do to Jesus for making Himself equal with God.

But in fact, Jesus in His teaching presented not only Himself as equal with God the Father but also the Holy Spirit being equal with God the Father and God the Son. In the Gospel reading, Jesus says the Spirit does something only God can do: namely, bring someone into the Kingdom of God by giving them new birth in Holy Baptism as God's beloved, holy children. Only God can give new life and grant admittance into His own Kingdom, and that is the Spirit's work.

God the Holy Spirit also was doing His unique work for our salvation when He brought the only-begotten Son of God into the world, as we confess in the Apostles' Creed that Jesus "was conceived by the Holy Ghost" and in the Nicene Creed that Jesus "was incarnate by the Holy Ghost of the Virgin Mary and was made man."

Once I was teaching the Christian Faith to a gentleman who asked, "If Jesus is God's Son, how is He also God?" That is a great question, and it is precisely what the creeds answer when they distinguish between the eternal begetting of the Son of God by His Father and the incarnation of the Son of God by the Holy Spirit, when the Man Jesus was conceived by the Holy Spirit and born of the Virgin Mary.

We confess in the Nicene Creed that the Jesus Christ is "the only-begotten Son of God, begotten of His Father before all worlds…begotten, not made." To beget means to become a father; to bear means to become a mother. We are begotten of our fathers; we are born of our mothers. In eternity, God the Father begat God the Son. This did not happen after the world was created, but in eternity. This is a mystery that we cannot even begin to explain; we can only confess it based on the teaching of God's Word that Jesus is the only-begotten Son of God, the completely unique and only Son of the Father.

But the begetting of the Son of God in eternity is different than His conception by the Holy Spirit in the womb of the Virgin Mary two thousand years ago. Like the creation of the world, the enfleshment of the Son of God was an act of the Trinity in time, not before time. The Father sent the Son into the world; the Son obeyed His Father's will and came down from heaven; the Holy Spirit enfleshed the Son in the womb of the Virgin Mary. This is how the Word who is God was made flesh and dwelt among us. And because the Son was conceived by the Holy Spirit, the Man Jesus was born without sin. And then this sinless God-Man, the spotless Lamb of God, went on to accomplish everything necessary to give eternal life to us sinners so that we too might become children of God. Unlike the Son of God, we are not God's children by nature, but we become God's children by adoption into the Holy Trinity in Holy Baptism, our rebirth into the Kingdom of God by water and the Spirit as we heard about in our Gospel reading.

So one of the things we celebrate on Trinity Sunday is our Baptism. In fact, the Small Catechism teaches us to begin and end our days remembering our Baptism into the Holy Trinity; when we get up and when we go to bed, we are to make the sign of the Holy Cross and say "In the Name of the Father and of the Son and of the Holy Spirit." And we should recall that our Baptism is an act of the Trinity, even as Christ's Baptism was, though His was not undergone for His own rebirth but in order to save us. He began His ministry by receiving John's baptism of repentance for the forgiveness of sins, expressing solidarity with us sinners even though He had no sin of His own. In the water He was identified by the Father as the Servant of the Lord who would bear the sins of the world. Then the Holy Spirit descended like a dove and was given to Him without measure to accompany Him as He overcame the temptations of the devil for us. By resisting Satan and living a sinless life in our place, the Son perfectly fulfilled God's Law. And finally the Son would willingly lay down His life on the cross to satisfy the Father's wrath against the sin of the world.

This is what Jesus describes in our Gospel reading when He says, "As Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, that whoever believes in him may have eternal life." After God had sent the fiery serpents as a punishment on Israel, God told Moses to lift up the serpent on a pole so that all the Israelites who had been bitten would not die but live. Similarly, Jesus is saying in the Gospel reading that now the Father would lift the Son up on the cross as a sacrifice for the sin of the world so that all who look to Him in faith may have everlasting life.

God loved the world this way: He gave His only-begotten Son into death on the cross, and out of perfect love for His Father, the Son laid down His life to save the world. Jesus described the universal nature of His death when He proclaimed, "When I am lifted up from the earth, I will draw all people to myself" (John 12:32). He said this to show how all-encompassing His death on the cross for sin was-not just for some, but for all people, His flesh and blood given for the life of the world.

And in His lifting up from the earth on the cross, we can see the divinity of the Son of God and the good will of God the Father toward sinners, as Jesus said to the Jews who would kill Him, "When you have lifted up the Son of Man, then you will know that I am he [that is, I am (ego eimi) the Lord], and that I do nothing on my own authority, but speak just as the Father taught me. And he who sent me is with me. He has not left me alone, for I always do the things that are pleasing to him" (John 8:28-29).

The Father's pleasure was in the Son's sacrificial death, as Jesus said, "For this reason the Father loves me, because I lay down my life that I may take it up again. No one takes it from me, but I lay it down of my own accord. I have authority to lay it down, and I have authority to take it up again. This charge I have received from my Father" (John 10:17-18).

Jesus obeyed His Father's charge. He laid His life down and through the Holy Spirit offered Himself to the Father as the once-and-for-all sacrifice for the sins of the world, and on the third day the Father raised Him from the dead, declaring His satisfaction with His Son's sacrifice and opening the kingdom of God to all believers.

And so for you who have been baptized, who have been born of God by water and the Holy Spirit, you have already entered the Kingdom of God, the Kingdom where your King has died and risen for you so that His death and resurrection are now your death and resurrection. "For the death He died He died to sin, once for all, but the life He lives He lives to God" (Romans 6:10).

So also you live. Even though your body will die, you are alive with an indestructible life given by the Holy Trinity. Jesus said, "For as the Father has life in himself, so he has granted the Son also to have life in himself" (John 5:26). "For as the Father raises the dead and gives them life, so also the Son gives life to whom he will" (John 5:21). And to you the Son proclaims, "It is the Spirit who gives life; the flesh is no help at all. The words that I have spoken to you are Spirit and life" (John 6:63).

Those Holy Spirit-filled words of life have been spoken to you in Baptism: "I baptize you in the name of the Father and of the Son and of the Holy Spirit." And in Holy Absolution: "I forgive you all of your sins in the name of the Father and of the Son and of the Holy Spirit." Those are the Trinity's Words to you, so repent and believe the Gospel, and then lift up your voices in praise to your Creator, Redeemer, and Sanctifier, the Father, Son, and Holy Ghost: "Blessed be the Holy Trinity and the undivided Unity. Let us give glory to Him because He has shown His mercy to us." Glory be to the Father and to the Son and to the Holy Ghost; as it was in the beginning, is now, and ever shall be, world without end. Amen.

And the peace of God which passes all understanding will keep your hearts and minds in Christ Jesus unto life everlasting. Amen.