One God, Three Persons

How do you talk to someone who can’t be fully understood?

How do you worship a God whose very nature exceeds your mental capacity to comprehend?

How do you build your entire life on a truth that you can affirm but never fully explain?

These aren’t theoretical questions—they’re the questions every Christian must answer when we encounter the doctrine of the Trinity. And this morning, as we continue our series through PBC’s Constitutional Doctrines, we come to the second statement of faith: the Godhead.

Let me read it for you from our church constitution:

“We believe that the Godhead eternally exists in three persons—the Father, the Son, and the Holy Spirit—and that these three are one God, co-equal and co-eternal, having precisely the same nature and attributes, and worthy of precisely the same worship, confidence, and obedience.”

Now, if you’re sitting here thinking, “That sounds complicated,” you’re in good company. One theologian said, tongue firmly in cheek, “The Trinity is a matter of five notions or properties, four relations, three persons, two processions, one substance or nature, and no understanding.”

But here’s the thing—and this is crucial—the Trinity isn’t a puzzle to be solved; it’s a mystery to be embraced. It’s not a philosophical riddle invented by clever theologians; it’s a revealed truth given by God Himself in His Word. Charles Ryrie, in his systematic theology, reminds us: “The doctrine of the Trinity is true because it is revealed in Scripture, not because we can fully comprehend it.” And far from being merely theoretical, the Trinity is profoundly practical. It transforms how we pray, how we worship, how we understand salvation, and how we live as the church.

This morning, I want to show you three things: First, how the Old Testament establishes the foundation for understanding God as one yet mysteriously complex. Second, how Jesus Christ reveals the Father and promises the Spirit, making the Trinity explicit. And third, how the early church formulated this doctrine to preserve the apostolic faith against dangerous distortions.

By the end of our time together, you’ll see that the Trinity isn’t a theological abstraction—it’s the beating heart of everything we believe about God and everything we experience in our relationship with Him.

Let’s pray, and then we’ll open God’s Word together.

POINT 1: The Old Testament Establishes the Foundation

Turn with me to Deuteronomy chapter 6, and I want us to look at verse 4 together. This is called the Shema—it’s the most important declaration of faith in all of Judaism. For three thousand years, faithful Jews have recited these words twice daily. Listen to what Moses says:

“Hear, O Israel: The LORD our God, the LORD is one.”

Six Hebrew words. That’s all. But packed into these six words is the bedrock truth upon which everything else is built: There is one God. Not two gods. Not a pantheon of gods. Not a divine council of competing deities. One God. Period.

Israel was surrounded by polytheism. Egypt had hundreds of gods. Canaan had Baal and Asherah and Molech. The nations worshiped the sun, the moon, the stars, fertility, war, death—you name it, they had a god for it. And into that world, God thunders through Moses: “Hear, O Israel—YHWH is our God, YHWH is ONE.”

This is foundational. You cannot understand the Trinity without first understanding monotheism. We do not worship three gods. We worship one God. The Trinity is not “God the Father, God the Son, and God the Holy Spirit” as if they’re three separate deities. No—the Trinity is one God eternally existing as three persons.

But here’s what’s interesting. Look at that word “one” in your English Bible—in Hebrew, it’s the word echad. And this matters more than you might think.

The Hebrew language has two words that can mean “one.” There’s yachid, which means “only, sole, solitary”—absolute singularity with no complexity whatsoever. And there’s echad, which means “one” but can include unified complexity.

Let me show you what I mean. Turn back to Genesis 2:24. Here’s what it says:

“Therefore a man shall leave his father and his mother and hold fast to his wife, and they shall become one flesh.”

What word is used there for “one”? It’s echad. Two persons—a husband and a wife—becoming “one flesh.” They don’t cease to be two distinct persons. The husband doesn’t disappear into the wife. They remain two individuals. But they’re united in such a profound way that Scripture calls them “one.”

That’s echad—unified oneness.

Here’s another example. In Genesis 11:6, at the Tower of Babel, God says, “Behold, they are one people, and they have all one language.” Same word—echad. Many individuals, one unified people. Many speakers, one unified language.

You see, echad is the standard Hebrew word for “one,” but it doesn’t demand absolute, isolated singularity. It allows for—and often expresses—unified complexity.

Now here’s the fascinating thing: When Moses wrote Deuteronomy 6:4, he could have used yachid if he wanted to emphasize that God is absolutely singular with no internal complexity whatsoever. But he didn’t. Under the inspiration of the Holy Spirit, Moses chose echad.

Now, does that prove the Trinity? No—not by itself. The doctrine of the Trinity isn’t explicitly taught in Deuteronomy 6:4. But what it does do is create linguistic space for the fuller revelation that would come later. It’s as if God is saying, “Yes, I am one. But don’t think my oneness is simplistic. There’s more to my nature than you yet understand.”

And there are other hints in the Old Testament—tantalizing glimpses that something complex is going on within the unity of God.

Turn back to Genesis 1:26. Here’s God at the moment of creating humanity:

“Then God said, ‘Let us make man in our image, after our likeness.'”

Did you catch that? “Let us make man in our image.” Why the plural pronouns? Some say it’s the “royal we”—the way a king might say “we” even when referring to himself alone. Others say God is addressing the angels. But look at verse 27:

“So God created man in his own image, in the image of God he created him.”

It switches back to singular. And humans are made in God’s image, not angels’ image. The most natural reading is that there’s something going on within the Godhead itself—some kind of internal conversation, some plurality within the divine unity.

The same thing happens in Genesis 3:22: “Then the LORD God said, ‘Behold, the man has become like one of us.'” And again at Babel in Genesis 11:7: “Come, let us go down and confuse their language.”

Over and over, there are these hints—these whispers—that God’s oneness is not simple isolation but complex unity.

And then there’s the Angel of the LORD. Throughout the Old Testament, there’s this mysterious figure who appears to people—to Hagar, to Abraham, to Moses, to Gideon—and He’s called “the Angel of the LORD,” but He’s also identified as the LORD Himself. He speaks as God, receives worship as God, and yet is somehow distinct from God.

The Old Testament saints didn’t have the vocabulary to explain this. They didn’t have our technical theological terms. But they knew—they knew—that their God was one, yet mysteriously more than what simple oneness might imply.

Think of it this way. Imagine trying to explain color to someone who’s been blind from birth. You could say “red is like this” and “blue is like that,” but you couldn’t make them see. The best you could do is give hints, use analogies, prepare them for the day when their eyes might be opened.

That’s what God was doing in the Old Testament. He was preparing Israel—and through Israel, preparing the world—for a fuller revelation. He established the foundation: ONE GOD. But He left room for the complexity: THREE PERSONS.

The Old Testament establishes the foundation. One God. Absolute monotheism. But even as it affirms God’s unity, it hints at something richer, something deeper, something that would be fully revealed when God Himself stepped into human history in the person of Jesus Christ.

POINT 2: Jesus Reveals the Father and Promises the Spirit

And that brings us to the New Testament. Because everything changes when Jesus shows up. The hints become explicit. The whispers become declarations. The foundation laid in the Old Testament now supports the full structure of Trinitarian theology.

Let me take you to the moment when Jesus begins His public ministry. Turn to Matthew 3, verse 16. Jesus has just been baptized by John in the Jordan River, and watch what happens:

“And when Jesus was baptized, immediately he went up from the water, and behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him; and behold, a voice from heaven said, ‘This is my beloved Son, with whom I am well pleased.'”

Do you see it? All three persons of the Trinity are present at the same moment, in the same event, yet clearly distinguished from one another.

The Son is standing in the Jordan River, water dripping from His hair, His humanity on full display.

The Spirit is descending from heaven in visible form, resting upon the Son.

And the Father is speaking from heaven, declaring His pleasure in the Son.

Three persons. One God. All active simultaneously. All working together. All distinct yet unified in purpose and action.

This destroys one of the oldest heresies about the Trinity—modalism, the idea that Father, Son, and Holy Spirit are just different modes or masks that the one God wears at different times. No. Here at Jesus’ baptism, we see them all at once. The Father isn’t pretending to be the Son. The Son isn’t pretending to be the Spirit. They’re three distinct persons in perfect relationship.

And Jesus doesn’t leave us guessing about His relationship to the Father. He makes claims that are either profoundly true or completely blasphemous—there’s no middle ground.

In John 10:30, Jesus says, “I and the Father are one.” The Jews around Him immediately picked up stones to kill Him because they knew exactly what He meant. In verse 33, they say, “It is not for a good work that we are going to stone you but for blasphemy, because you, being a man, make yourself God.”

Jesus claimed deity. Clearly. Repeatedly. Unambiguously.

In John 8:58, He says, “Before Abraham was, I AM”—using the divine name, the name God revealed to Moses at the burning bush. The Jews tried to stone Him for that too.

In John 14:9, Philip asks Jesus to show them the Father, and Jesus responds, “Whoever has seen me has seen the Father.” Not “I’ll show you the Father.” Not “Let me describe the Father to you.” But “If you’ve seen me, you’ve seen Him.”

Jesus is God. Fully God. Not a created being. Not a demigod. Not an exalted angel. God in human flesh. The second person of the Trinity, eternally begotten of the Father, one in essence with the Father.

But here’s the beautiful complexity: Jesus is distinct from the Father. He prays to the Father. He submits to the Father’s will. He says in John 14:28, “The Father is greater than I”—not in essence or deity, but in His role during the incarnation.

Theologians distinguish between two aspects of the Trinity: the ontological Trinity—who God is eternally in His very nature—and the economic Trinity—how the three persons function in the work of redemption. Ontologically, the Son is fully equal to the Father in essence, power, and glory. Economically, the Son voluntarily submits to the Father’s redemptive plan. This is functional subordination in His incarnation role, not eternal subordination of essence.

The Son took on human flesh; the Father remained transcendent in heaven. The Son submitted to the Father’s redemptive plan; the Father sent the Son. But never mistake role for nature. The One who washed feet is the One who created galaxies.

Distinction of persons. Unity of essence. One God, multiple persons.

And then Jesus promises a third person—the Holy Spirit. In John 14:16, He says to His disciples:

“And I will ask the Father, and he will give you another Helper, to be with you forever.”

That word “another” is crucial. In Greek, there are two words that can mean “another.” There’s heteros, which means “another of a different kind,” and there’s allos, which means “another of the same kind.” Jesus uses allos. He’s saying, “I’m going to send you another Helper who’s just like me—same nature, same divine essence, same kind of person.”

And in verse 26, He makes it even clearer:

“But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things.”

Notice the personal pronouns. Not “it will teach you” but “he will teach you.” The Holy Spirit is not an impersonal force, not just divine energy or power. He’s a person. He can teach. He can testify (John 15:26). He can be grieved (Ephesians 4:30). He has a mind, a will, emotions—everything that makes someone a person.

And notice the Trinitarian structure: The Father will send the Spirit in the Son’s name. All three persons. Distinct yet united. Working together in perfect harmony to accomplish our salvation.

You see, what Jesus does in the Upper Room Discourse—those incredible chapters in John 14, 15, and 16—is pull back the curtain on the inner life of God. He shows us that there are eternal relationships within the Godhead. The Father loves the Son. The Son glorifies the Father. The Spirit proceeds from the Father and testifies about the Son. These aren’t temporary roles they’re playing for our benefit. These are eternal realities of who God is.

God is not a lonely monad—isolated, solitary, needing to create in order to have someone to love. No, God is eternally relational within Himself. Before the foundation of the world, before there were angels or humans or any created thing, the Father loved the Son in the fellowship of the Spirit. God is love not just in His actions toward us but in His very nature—eternally existing as three persons in perfect love, perfect communion, perfect unity.

And here’s why this matters: When you became a Christian, you weren’t just added to God’s to-do list. You were invited into the eternal fellowship that has existed within the Trinity from all eternity. Jesus prays in John 17:21, “That they may all be one, just as you, Father, are in me, and I in you, that they also may be in us.”

You’re not just learning about the Trinity. You’re living in relationship with the Trinity. You’re experiencing the Father’s love, the Son’s grace, and the Spirit’s fellowship every single day of your Christian life.

POINT 3: The Church Formulates Trinitarian Theology

Now, if the Trinity is so clearly taught in the New Testament, why did it take the early church several centuries to formulate precise creeds and doctrinal statements about it?

That’s a fair question, and the answer is important: It’s because people started getting it wrong.

As long as the apostles were alive, their teaching provided a living standard against which error could be measured. But once the apostolic era ended, false teachers began to twist the biblical data in dangerous ways.

Some, like Arius in the fourth century, said Jesus was the first and greatest created being but not truly God. This destroyed the gospel—if Jesus isn’t fully God, His death can’t save us from the wrath of a holy God. Only God can bear infinite wrath; only God can provide infinite satisfaction for sin.

Others, like the Sabellians, said there’s only one divine person who wears different masks at different times—sometimes appearing as Father, sometimes as Son, sometimes as Spirit. This destroyed the gospel too—if the Father is the same person as the Son, then who was Jesus praying to in the Garden of Gethsemane? Himself? The Cross becomes a divine monologue rather than the Son’s loving submission to the Father’s will.

Still others, called tritheists, said there are three separate gods who just happen to work together really well. This destroyed biblical monotheism—suddenly we’re no different than pagans with a pantheon.

The church had to respond. Not by inventing new doctrines, but by carefully stating what the Bible actually teaches in a way that excluded these dangerous distortions.

And that brings us to our main text for this morning. Turn with me to 2 Corinthians 13:14. This is how Paul ends his second letter to the Corinthians:

“The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.”

This is called the Apostolic Benediction, and it’s the only Pauline benediction that explicitly names all three persons of the Trinity. And notice what Paul does here—he puts all three persons in coordinate relationship with one another.

He begins with Christ’s grace. Why? Because that’s how you experience God—through Jesus Christ. You don’t start with philosophical speculation about the nature of God; you start with the historical person Jesus Christ who died on a cross and rose from the dead. You encounter grace—undeserved favor, unmerited blessing, forgiveness you could never earn—and that grace flows from Christ.

Then Paul moves to the Father’s love. Why does Christ show you grace? Because of the Father’s love. John 3:16 says, “For God so loved the world, that he gave his only Son.” The Father’s love is the fountain from which all salvation flows. It’s the Father who planned redemption, who chose you before the foundation of the world, who predestined you for adoption as His child.

And finally, Paul mentions the Spirit’s fellowship. The Greek word is koinonia—communion, sharing, intimate participation. It’s the Holy Spirit who makes the Father’s love and the Son’s grace real in your experience. It’s the Spirit who indwells you, transforms you, gives you assurance that you’re a child of God.

Three persons. Three distinct roles in your salvation. Yet one unified work of one God.

And Paul isn’t inventing this. He’s simply reflecting what all the apostles understood. Turn to Matthew 28:19. This is the Great Commission—Jesus’ final command to His disciples before ascending to heaven:

“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.”

Notice: “in the name”—singular. Not “names,” as if each person has their own separate name. One name. Because there’s one God.

But that one name belongs to three persons: Father, Son, and Holy Spirit. All three mentioned together. All three coordinate. All three worthy of equal honor.

This is Trinitarian baptism. You’re baptized into the name of the triune God. You belong to the Father who chose you, the Son who redeemed you, and the Spirit who seals you.

The early church took this seriously. From the very beginning, from the book of Acts onward, Christians baptized in the threefold name. The Didache, an early Christian manual dating to the late first century, gives instructions for baptizing “in the name of the Father and of the Son and of the Holy Spirit.” Ignatius, Tertullian, Hippolytus—all the early church fathers echo this formula.

But by the time you get to the Council of Nicaea in AD 325, the church had to get more precise. Arius was teaching that Jesus was created. The church had to respond: “No—Jesus is ‘begotten, not made, being of one substance with the Father.'”

That phrase—”of one substance”—used a Greek word, homoousios, that’s not in the Bible. And some Christians objected: “We shouldn’t use non-biblical terms!”

But Athanasius, the great defender of orthodoxy, had a brilliant response: “The Arians are evading biblical terminology. They’ll affirm biblical words while denying biblical meaning. So we need a precise term that they can’t wiggle out of.”

And here’s the principle: The church can use extra-biblical terms as long as those terms accurately express biblical truth. We say “Trinity” even though that word isn’t in the Bible. We say “incarnation” even though that word isn’t in the Bible. We say “inerrancy” and “dispensationalism” and “substitutionary atonement”—all extra-biblical terms that express biblical realities.

The Nicene Creed wasn’t inventing doctrine. It was defending doctrine. It was drawing a line in the sand and saying, “This is what the Bible teaches. Anything else is heresy.”

And what it teaches is this: One God, eternally existing in three persons—Father, Son, and Holy Spirit—co-equal, co-eternal, co-essential. Each fully God. Each distinct from the others. Yet only one God.

Here’s an illustration that might help, though like all illustrations, it breaks down if you push it too far. Think about Athanasius facing off against Arius. Arius had the emperor’s ear. He had political power. He had eloquence and charm. And he was teaching that Jesus was created, not eternal.

Athanasius was short, unimpressive to look at, and spent more than twenty years in exile for his beliefs. Five times he was driven from his home church in Alexandria. But he refused to compromise.

And here’s why: Athanasius understood that if Jesus isn’t fully God, then we’re not fully saved. If Jesus is a creature—no matter how exalted—then His death is the death of a creature, and it can’t pay the infinite debt we owe to an infinite God. Only God can save. Jesus saves us. Therefore, Jesus must be God.

The Trinity isn’t a philosophical puzzle. It’s the heartbeat of the gospel. Get the Trinity wrong, and you lose the gospel. Get the Trinity wrong, and you lose assurance, you lose worship, you lose hope.

But get the Trinity right—embrace it even though you can’t fully comprehend it—and suddenly everything else comes into focus.

CONCLUSION & APPLICATION

So how does the Trinity transform everything?

Let me give you four quick applications as we close.

First, the Trinity transforms your prayer life. You pray to the Father, through the Son, in the Spirit. When you pray, all three persons are involved. The Father hears you. The Son intercedes for you at the Father’s right hand (Romans 8:34). And the Spirit helps your weakness, interceding with groanings too deep for words (Romans 8:26).

You’re never praying alone. You’re never stumbling around trying to find God. The triune God is working to bring you into His presence.

Second, the Trinity transforms your assurance. You’re not saved by your own effort. You’re saved by the coordinated work of Father, Son, and Spirit. The Father chose you before the foundation of the world. The Son died for you and declared “It is finished.” The Spirit sealed you as a guarantee of your inheritance.

Now think about this: If the Father’s choice could be revoked, you’d be lost. If the Son’s work could be undone, you’d be lost. If the Spirit’s sealing could be broken, you’d be lost. But your salvation rests on the triune God—eternal, unchanging, all-powerful. Can God change His mind? Can God fail? Can God break His promise? The nature of the Trinity itself guarantees your eternal security. You are as secure as God Himself, because your salvation is grounded in who He is, not in what you do.

Third, the Trinity transforms your worship. You don’t worship a distant, unknowable deity. You worship a God who is eternally relational, eternally loving, eternally glorious. When you sing “Holy, Holy, Holy, Lord God Almighty,” you’re echoing the worship of the seraphim who cry out before the triune throne. When you pray “Our Father,” you’re entering the same relationship the eternal Son has with the Father. When you walk in the Spirit, you’re participating in the same eternal fellowship that has existed within the Godhead forever.

Fourth, the Trinity transforms your relationships. The church is meant to reflect the Trinity—unity in diversity, love in submission, equality in function. When we love each other as Christ loved us, when we serve one another in humility, when we maintain the unity of the Spirit in the bond of peace, we’re imaging the triune God to a watching world.

Let me close with this. You don’t have to fully understand the Trinity to be saved. You don’t have to be able to explain it perfectly to worship God rightly. But you do need to affirm what the Bible teaches: One God, three persons, equally worthy of your worship, your confidence, and your obedience.

And here’s the promise: The same God who revealed Himself in Scripture—the Father who loved you, the Son who died for you, and the Spirit who lives in you—that God is with you right now. His grace, His love, and His fellowship are yours.