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Objective

In this lesson, we’ll discover how God has revealed Himself in Scripture as one God who exists eternally in three distinct Persons—Father, Son, and Holy Spirit.

Key Verse

Deuteronomy 6:4: Hear, O Israel: The Lord our God, the Lord is one.

Introduction

The Bible declares clearly that there is only one God. Yet the Bible also declares with equal clarity that Jesus Christ is God and that the Holy Spirit is God. How can this be? How can God be one and three at the same time?

This question has challenged believers for centuries, yet it stands at the very heart of our Christian faith. The doctrine we call the Trinity—that God exists as one Being in three Persons—is not a contradiction to be solved but a mystery to be embraced and worshiped.

When the ancient Israelites heard the words of Deuteronomy 6:4, they called it the Shema—from the Hebrew word meaning “hear.” To this day, Jews who observe the Old Testament law view this statement as their confession of faith. They understand that this declaration sets the true God apart from all the false gods that surround them.

We live in a world that worships many gods, just as the Israelites did. Some people bow down to idols made of wood and stone. Others worship the gods of money, power, and pleasure. But God calls us to bear witness to the truth: there is one God who created us, loves us, and has revealed Himself perfectly in Jesus Christ.

In this lesson, we’ll explore together these important truths:

• God is one God
• God exists as three Persons

The Unity of God

Satan’s desire has always been to lead people away from the one true God—the One who made heaven and earth. In the Old Testament, the Children of Israel were constantly tempted to follow false gods. The Canaanites worshiped Baal, whom they believed controlled the weather and crops. The Ammonites sacrificed their children to Molech, hoping to gain his favor through horrific acts.

But God called His people out of this darkness to bear witness to a completely different reality. Unlike these false gods, who were described in Scripture as being like a “vapor” or “mist”—something that lacks substance—the true God is real, eternal, and unchanging. This is the same word used in Ecclesiastes (hebel in the Hebrew) to describe “vanity” or “emptiness.” That’s exactly what false gods are like: they’re not real. They have no power to help, no ability to save, no genuine existence at all.

Deuteronomy 6:4: Hear, O Israel: The Lord our God, the Lord is one.

This simple yet profound statement established Israel as unique among all the nations. While everyone around them worshiped many gods, Israel proclaimed that there is only one true God. This was revolutionary thinking in the ancient world, where people believed that different gods controlled different areas of life.

Isaiah 43:10-11: “You are my witnesses,” declares the Lord, “and my servant whom I have chosen, so that you may know and believe me and understand that I am he. Before me no god was formed, nor will there be one after me. I, even I, am the Lord, and apart from me there is no savior.”

The early Christians faced the same challenge. When the gospel was first preached, it went out to people who worshiped many false gods. The city of Athens, where Paul preached, was full of idols dedicated to various deities (Acts 17:16). But Paul boldly proclaimed the truth about the one true God who created all things and doesn’t need anything from us.

Acts 17:24-25: The God who made the world and everything in it is the Lord of heaven and earth and does not live in temples built by human hands. And he is not served by human hands, as if he needed anything. Rather, he himself gives everyone life and breath and everything else.

The same is true for us today. We are called to be witnesses that there is one God who created us and revealed Himself to us in Christ. We bear witness to this truth before those who worship false gods—whether these are the gods of rivers and trees that some cultures honor, or the gods of power, money, and pleasure that dominate our modern world.

Paul describes idolatry as “ignorant worship.” We were created to worship God, and yet we turn away from His clear revelation of Himself. If we don’t worship the one true God, we will always worship something else.

✏️ Notebook Moment. What are some “false gods” that tempt people in your culture? What false gods are most tempting to you? What does God give us that these false gods never can?

The Trinity

The word “Trinity” is not found anywhere in the Bible, but the doctrine of the Trinity is a biblical truth that flows from every page of Scripture. It is one of the foundational doctrines of the Christian faith. From the very beginning of the church, Christians have confessed that God the Father, God the Son, and God the Holy Spirit are one God existing in three distinct Persons.

➤ The Trinity in the Old Testament

Though the Trinity is more fully revealed in the New Testament, there are clear hints of this doctrine throughout the Old Testament. These hints show us that God was preparing His people to understand the fuller revelation that would come through Jesus Christ.

First, one of the names of God, Elohim, is actually a plural word. When we read in Genesis 1:26, “Let us make mankind in our image,” God is speaking as more than one Person while remaining one God.

Second, the Hebrew word that describes how God is “one” in Deuteronomy 6:4 can describe something that has unity while containing multiple parts. In Genesis 2:24, this same word describes how a husband and wife become “one flesh”—they remain two distinct people while becoming one in marriage.

Third, we see appearances of a mysterious Person in the Old Testament who looks like a man but speaks and acts like God. This Person is called the “Angel of the Lord,” and He appears throughout Israel’s history.

Exodus 3:2-4: There the angel of the Lord appeared to him in flames of fire from within a bush. Moses saw that though the bush was on fire it did not burn up. So Moses thought, “I will go over and see this strange sight—why the bush does not burn up.” When the Lord saw that he had gone over to look, God called to him from within the bush, “Moses! Moses!”

Notice that the Angel of the Lord is identified as God Himself. This same pattern appears when the Angel of the Lord spoke to Gideon, calling him to deliver Israel from their enemies. The Angel of the Lord is referred to as God, yet He is also distinguished from God in heaven. We believe this is the Son of God appearing in the Old Testament, before He came to earth as a man.

Fourth, the prophecies about a coming Son make it clear that He would be equal with the Lord Himself.

Isaiah 9:6: For to us a child is born, to us a son is given, and the government will be on his shoulders. And he will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace.

How could a child who is born also be called “Mighty God” and “Everlasting Father”? This prophecy points us toward the mystery of the Trinity—the Son is fully God while being distinct from the Father.

Fifth, all three Persons of the Trinity can be seen clearly in Isaiah 63:9-10. The passage speaks of the Lord in heaven, the Angel of His Presence who saved them, and the Holy Spirit whom they grieved through their rebellion. Here we see Father, Son, and Holy Spirit working together in Israel’s history.

The angels around God’s throne sing “Holy, Holy, Holy” three times as a way of honoring the perfect holiness of God. But this threefold declaration may also reflect the Trinity—three Persons sharing one divine nature of perfect holiness.

➤ The Trinity in the New Testament

The doctrine of the Trinity is revealed much more clearly in the New Testament. Jesus Himself speaks of the Father, the Son, and the Holy Spirit as distinct Persons who are equally God.

One of the clearest pictures of the Trinity appears at the baptism of Jesus. In this remarkable scene, we see all three Persons of the Trinity present and active at the same time.

Matthew 3:16-17: As soon as Jesus was baptized, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and alighting on him. And a voice from heaven said, “This is my Son, whom I love; with him I am well pleased.”

Here we see the Son being baptized in the water, the Holy Spirit descending from heaven like a dove, and the Father speaking from heaven. All three Persons are clearly present, yet they are working together in perfect unity to mark the beginning of Jesus’ public ministry.

Matthew 28:19: Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.

Notice that Jesus says “in the name”—singular—of three Persons. This shows us that the Father, Son, and Holy Spirit share one divine name and nature while being three distinct Persons.

The New Testament clearly declares that the Father is God, the Son is God, and the Holy Spirit is God, while maintaining that there is only one God. This might seem impossible to understand, but Scripture teaches this truth through specific passages that identify each Person of the Trinity as fully God. Let’s look at how the Bible establishes the divine nature of each Person.

The Father is clearly identified as God in passages like this one:

John 6:27: Do not work for food that spoils, but for food that endures to eternal life, which the Son of Man will give you. For on him God the Father has placed his seal of approval.

The Son is directly called God by the Father Himself:

Hebrews 1:8: But about the Son he says, “Your throne, O God, will last for ever and ever; a scepter of justice will be the scepter of your kingdom.”

The Holy Spirit is shown to be God through this powerful encounter with Peter:

Acts 5:3-4: Then Peter said, “Ananias, how is it that Satan has so filled your heart that you have lied to the Holy Spirit and have kept for yourself some of the money you received for the land? Didn’t it belong to you before it was sold? And after it was sold, wasn’t the money at your disposal? What made you think of doing such a thing? You have not lied just to human beings but to God.”

Peter says that lying to the Holy Spirit is the same as lying to God—showing us that the Holy Spirit is fully God.

Understanding This Divine Mystery

How can God be one and three at the same time? In struggling to understand this divine mystery, people can easily fall into serious errors. It’s important that we avoid three false teachings about the Trinity.

First, there are those who completely deny that God is Three in One. They believe only in God the Creator and deny that Jesus Christ and the Holy Spirit are truly God. This error has existed in the church from the earliest times and continues today.

Second, there are those who believe that the Trinity means there are actually three separate Gods rather than one God who exists in three Persons. This makes Christianity no different from the pagan religions that worship multiple deities.

Third, there are those who believe that Jesus Christ and the Holy Spirit are just different “expressions” or “modes” of God’s being. They think God has revealed Himself in different ways but that the Father, Son, and Holy Spirit are not truly distinct Persons.

We can try to understand the Trinity, but we will never fully grasp its depth in this life. Our understanding will always be limited and incomplete. This is not a weakness in the doctrine but a reminder that God is infinitely greater than our minds can contain.

No example from nature is sufficient to fully explain the Trinity, but some helpful illustrations can point us in the right direction. For instance, consider the sun. We can never approach the sun directly—it would destroy us. As the Bible says, God “lives in unapproachable light” (1 Timothy 6:16). We can only know the sun as its light comes to us. Jesus is the light of the world (John 8:12), sent from the Father to reveal God to us. Along with the light, we receive the energy and warmth of the sun, which reminds us of the work of the Holy Spirit in bringing life and power to our hearts.

(Notebook Moment: What questions do you have about the Trinity? How does it help you to know that this doctrine is a mystery that even the greatest Christian thinkers have never fully understood?)

Of course, this is an imperfect example. No earthly illustration can capture the full mystery of the Trinity. But examples like this can help us understand how God can be Three in One without contradiction.

Why the Trinity Matters

You might wonder why the doctrine of the Trinity is so important. Why does it matter to our Christian faith? The answer is that the Trinity touches every aspect of our relationship with God.

Without the doctrine of the Trinity, we cannot understand how Jesus can be one with the Father. If Jesus is not truly God, then His death on the cross was just the death of a good man—it could not pay the penalty for our sins. Only God Himself could bear the infinite punishment that our rebellion deserved.

Without this doctrine, we cannot understand the person and nature of the Holy Spirit. If the Holy Spirit is not God, then He lacks the power to change our hearts, guide us into truth, and seal us for eternity. Our spiritual life depends on the Spirit being fully God.

Without this doctrine, we don’t fully understand what happened at the cross. When Jesus died for our sins, God was not punishing an innocent third party. Rather, God Himself was taking upon Himself the judgment that we deserved. The Father, Son, and Holy Spirit worked together in perfect unity to accomplish our salvation.

Finally, without this doctrine, we don’t understand that God experiences perfect fellowship within Himself. Before He created anything, the Father, Son, and Holy Spirit enjoyed perfect love and communication with each other. God invites us to share in this same fellowship through Jesus Christ.

John 17:21: That all of them may be one, Father, just as you are in me and I am in you. May they also be in us so that the world may believe that you have sent me.

1 John 1:3: We proclaim to you what we have seen and heard, so that you also may have fellowship with us. And our fellowship is with the Father and with his Son, Jesus Christ.

(Notebook Moment: How does knowing that God exists in perfect fellowship within the Trinity change your understanding of why He desires a relationship with you?)

Conclusion

The doctrine of the Trinity stands at the heart of everything we believe as Christians. It protects the truth about who God is and makes possible everything we know about salvation, spiritual life, and eternal fellowship with our Creator.

When we worship the Trinity, we are not worshiping a God who is lonely or incomplete. We worship the God who is perfect in Himself—Father, Son, and Holy Spirit dwelling in eternal love and perfect unity. This same God has opened His arms to welcome us into His family through the work of Jesus Christ.

The God who declared “Hear, O Israel: The Lord our God, the Lord is one” is the same God who sent His Son to die for our sins and His Spirit to live within us. He is one God, eternally existing in three Persons, working together to accomplish our salvation and bring us into fellowship with Himself.

As we continue to grow in our understanding of God’s Word, we will discover more and more how the Trinity appears in every aspect of our faith. The Father planned our salvation, the Son accomplished our salvation, and the Holy Spirit applies our salvation to our hearts. All three Persons work together in perfect harmony to bring us home to God.

This is the God we serve—not a distant, unknowable deity, but the loving Trinity who has revealed Himself to us and invited us to know Him personally through Jesus Christ. Let this truth fill your heart with wonder and your lips with praise!

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