This sermon was originally preached at Messiah Evangelical Lutheran Church in East Setauket, New York.

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In the name of Jesus, amen.  My brothers and sisters in Christ:  Today is Trinity Sunday, the Sunday on which we celebrate the mystery of who God is and confess our faith in that mystery using the words of the Athanasian Creed, named for the strong Trinitarian church father, St. Athanasius of Alexandria, but not actually written by him.  And what a creed!  When I was growing up, I always thought that it sounded like a mathematical proof.  But the Athanasian Creed goes into detail about who God is, how God is Father, Son, and Holy Spirit, not three gods, but one God in three persons.  The Father is God.  The Son is God.  The Holy Spirit is God.  But the Father is not the Son, nor is He the Spirit; the Son is not the Father or the Spirit, and the Spirit is not the Father or the Son.  Because we already said it, I won’t rehash it, but the Athanasian Creed can be a handy way to remember how the different persons of the Godhead relate to us and to one another.  Nonetheless, it can be difficult to see the Trinity in the Bible, and many people and religions have tried to understand it, have failed to get things right, or have denied that the Trinity exists outright.

For instance, way back in the early days of the Church, a North African priest named Arius denied that Jesus was God, instead calling him God’s chief creation because Arius couldn’t fathom that God would be willing to share his glory with anyone.  Arius’ theology was deemed a heresy by church councils, but it still crops up here and there, influencing various groups ranging from the Muslims, whose Qur’an denies that there is a plurality to the Godhead (Muhammad seemed to think that the Trinity was actually a form of polytheism, belief in multiple gods) to the modern-day Jehovah’s Witnesses, Unitarians, and Oneness Pentacostals.  Other groups have upheld Jesus’ divinity (or have given him a measure of divinity), but do not believe that the Holy Spirit is a separate person.  If you’ve driven through parts of eastern Pennsylvania, especially around Bethel, you’ve probably seen signs for the Assemblies of Yahweh, a sect that came out of the “Sacred Name Movement.”  In addition to putting the Son below God the Father, they also believe that the Holy Spirit “is the mighty power from the Heavenly Father and the Messiah dwelling within us” but not actually a person in his own right (I guess they take a figurative reading of the beginning of Genesis or the Spirit’s appearing at Jesus’ baptism).

But these views of God ignore certain things he reveals about himself in Scripture, or they attempt to make the mystery of God’s persons make sense to human minds.  Human minds like everything to be perfectly logical and understandable.  Of course, God is bigger than we are, and who he is truly a mystery.  That is to say, his nature and being is transcendent, beyond normal understanding, and, indeed, something of a secret which God has chosen to reveal to us in certain ways.  But being people, we would prefer blatant explanations rather than just letting the mystery be.  People want to be able to understand who God is on their own terms, not on God’s terms.  And, after all, our minds are limited by our own experience and perception, and the hows and whys of a God who exists outside of time and space are beyond our ken.

Indeed, sometimes the examples even pious Christians use to explain the Trinity miss the mark.  Do you all know the old story about how St. Patrick supposedly used a shamrock, a three-leaf clover, to teach the Trinity to the Irish?  How he said that the three leaves of the shamrock are each like a person of the Trinity?  Well, one hates to break it to St. Patrick, but that particular metaphor is incorrect.  In fact, it teaches a heresy called “partialism, ” which argues that the different persons of the Trinity are all “parts” of one whole divine entity; that each person is not wholly God, but together they make up God.  It’s a bit like that old show “Voltron,” where the five robot lions connect together to form one big fighting robot, or in Power Rangers where the different Zords come together to make the Megazord.  That’s partialism’s view of God, but that’s not how God has revealed himself in Scripture.  Or have you heard this example: that the Trinity is like water, which exists in three states of matter, solid (ice), liquid, and gas (vapor).  Well, that’s a heresy called “modalism,” where God is understood to change mode based on what he’s doing.  Of course this is not how God has revealed himself. In fact, if you take modalism to its furthest conclusion, you could argue that it was God the Father who died on the cross (another heresy called patripassionism, the belief that the Father suffered).  But again, this is not what God tells us in Scripture.  The Son suffered.  But that doesn’t stop human beings from trying to understand God on their own terms, even if it gets them thinking about God in the wrong way.  People want God to explain his being on their terms, but again, God instead presents himself on his own terms.  And his own terms are difficult to make sense of, but that’s why it is better to just let the mystery be.  Lutherans are no strangers to paradoxes.  But suffice it to say that the Athanasian Creed takes what God has revealed about himself and makes the most sense out of all of it.

In our Old Testament reading this morning, we find the Prophet Isaiah recounting how God called him to be his prophet.  Isaiah finds himself standing before the throne of God in the Temple in the presence of the Godhead.  Isaiah is terrified.  He’s in the presence of the Most High God.  This means that Isaiah should be dead.  He’s a human being, and humans cannot stand in the presence of God and live on account of their sins.  God’s holiness cannot abide sin, and if there’s any doubt, the two six-winged seraphim,  angels who look like flaming serpents, bellow back and forth these Hebrew words: “KADOSH, KADOSH, KADOSH.”  “Holy, Holy, Holy is the Lord of hosts; the whole earth is full of his glory!”  “Holy, Holy, Holy.”  Or we could translate it another way: “Separate, Separate, Separate” or “Unique, Unique, Unique.”  God is wholly other, wholly separate from sinful humanity, wholly pure.  A man of unclean lips from a people of unclean lips cannot exist in the presence of such holiness.  As God says, no one can look upon his glory and live.  An unclean man cannot enter into the presence of God on his own terms.  

But Isaiah has not been placed before the Almighty on his own terms.  Isaiah finds himself before the throne of God on God’s terms.  And when Isaiah finds himself before the throne of God, he finds himself alive on God’s terms.  God’s Triune terms.

In Isaiah 6, we see the Trinity at work.  “How so?” you might ask.  “Isaiah just speaks of seeing God, he doesn’t talk about a Trinity.”  First, notice that Isaiah never actually describes what God looks like.  He talks about everything around him—the smoke, the throne, the pavement, God’s robe, the seraphim bellowing “KADOSH KADOSH KADOSH” (which may indeed be pointing to each person of the Trinity!)–but he doesn’t say what God looks like.  I have to wonder what we’d be expecting with regard to seeing the Triune God as he is, though I think anything we can imagine would be in error. 

But how does Isaiah experience the Triune?  Remember, God the Father is all-holy ruler and judge.  Isaiah cannot stand before him as a sinner.  He is the one who has called Isaiah to be his prophet.  But Isaiah cannot do this holy work if he is unredeemed.  He must be made righteous, made whole.  So God the Son, Jesus, cleanses him through his saving, sacrificial work.   

The burning coal which cleanses Isaiah comes from the altar in the Temple.  In the Old Testament system of sacrifice, this is where sacrifices for sin took place, and the blood was sprinkled on the mercy seat of the Ark of the Covenant in the Temple’s Holy of Holies.  The Holy of Holies was understood to be God’s throne room on earth, and the mercy seat his throne.  This means that Isaiah is standing in the Holy of Holies!  The sprinkling of the blood signified God’s taking away sin.  But no sacrificial victim is seen here to be burned on the altar and to have its blood sprinkled on the Ark.  The sacrifice that takes away sin must be…God’s.  It still comes from Jesus: Isaiah receives the benefit of Jesus’ saving, cleansing work before Jesus’ incarnation, retroactively, as have all those in the Old Testament who held to the promises God made in his covenant with Israel.  Isaiah’s faith makes it so.  Because of Jesus, he can stand before God.

And, once Isaiah is cleansed by Jesus, God the Son, the second person of the Trinity, he is empowered by God the Holy Spirit to live as God’s man, to be holy, and to be able to heed God’s call: “Whom shall I send, and who will go for us?”  Cleansed from guilt, the redeemed, regenerated Isaiah can say, guided and strengthened by Holy Spirit, “Here I am! Send me!”  The Holy Spirit sanctifies him to be God’s mouthpiece and to grow as a cleansed righteous man.

This is how the Triune God works in our lives, too.  The Father creates and sustains us.  He gives us our callings, and calls us to be righteous as he is righteous.  The Son saves us—we, who are people of unclean lips— by justifying us and making us righteous through his death and resurrection which, for us, has happened in our time.  And the Holy Spirit “is sent to sanctify our minds, that is, to kindle new light, righteousness, and a life which is pleasing to God and is eternal for those who are the heirs of eternal life” (Melanchthon 1543, 21). God calls us just like he calls Isaiah, the Son makes us his, and the Holy Spirit enables us in those callings.  This is how the Triune God loves us, and he does it on his terms.  We contribute nothing to this way that God deals with us and calls us to be his people.  He does everything.  We respond.  This is how he loves us.

And so this Trinity Sunday, let’s think about how God calls us and sanctifies us.  What are we called to do?  God calls us to perform our vocations well as individuals and to serve our neighbors.  That means being a good father, a good mother.  A good son or daughter.  A good friend.  A good doctor,  lawyer, teacher, or pastor, or plumber. But what is he calling us to do as a congregation?  Who is he calling us to be?  How is he calling us to love other people?  To spread the Gospel?  Firm in the knowledge that the Triune God loves us, saves us, and sanctifies us, let us contemplate what God has in store for us as we embark on a summer of new possibilities and renewed opportunities to meet, praise our Lord, receive his gifts, enjoy fellowship with one another, and touch one another’s lives.   Amen!