Deuteronomy 6:4 (ESV) 4 “Hear, O Israel: The Lord our God, the Lord is one.
Do you know what heresy is? According to Dictionary.com, heresy is an opinion or doctrine at variance with the orthodox or accepted doctrine, especially of a church or religious system.
Most heresies start with how we view God. Imagine a two-year old trying to explain to another two-ear old what it means to be an adult. How accurate do you think that would be? It may have some truth, but it would probably have a lot that would make us laugh. That is what happens when we mere humans try to explain God. How can mortal humans with limited knowledge be able to explain an immortal God who has all knowledge?
So, where do find out about God? God has revealed (made himself known) to us through His Word. The problem is that too often we try to use human logic to understand the Word of God. We try to view God’s Word through our own human experiences. This is a problem for many reasons. One is that the Bible was written in a different time, culture, and context. To try to understand the Bible only by using our present-day culture and context will confuse us. We need to understand the culture and context that the Bible was written to understand the Bible.
One of the first rules for reading the Bible is to look for the clear and simple meaning. We get into all kinds of trouble when we ignore the simple meaning. This leads to heresy.
Deuteronomy 6:4 tells us that God is one. There is only one God. God is very clear that we should only worship the one true God. That is the first of the Ten Commandments. “You shall have no other gods before me.” But God also reveals Himself as three persons – Father, Son and Holy Spirit. Where do we find this?
Mark 1:9-11 (GW)
9 At that time Jesus came from Nazareth in Galilee and was baptized by John in the Jordan River. 10 As Jesus came out of the water, he saw heaven split open and the Spirit coming down to him as a dove. 11 A voice from heaven said, “You are my Son, whom I love. I am pleased with you.”
Jesus is called the Son of God. Here at His baptism we see Jesus being baptized. A voice speaks from heaven calling Jesus His Son. How do we know this is the Father? Jesus calls Him that many times throughout the Gospels. John 20:17 (GW) 17 Jesus told her, “Don't hold on to me. I have not yet gone to the Father. But go to my brothers and sisters and tell them, ‘I am going to my Father and your Father, to my God and your God.'”
How can Jesus call someone else His father if He is the Father? This would take quite some Scriptural gymnastics to understand Jesus as the Father who speaks about going to Himself.
Also, in Jesus’ baptism we see the Holy Spirit coming down as a dove. The Holy Spirit is not an emanation or power of God. The Holy Spirit is a unique person. Mark 13:11 (GW) 11 When they take you away to hand you over to the authorities, don't worry ahead of time about what you will say. Instead, say whatever is given to you to say when the time comes. Indeed, you are not the one who will be speaking, but the Holy Spirit will.
There are many more verses about God the Father, God the Son, and God the Holy Spirit. If you would like to research this for yourself, you can use an online Bible study tool like BibleGateway. Just type in words like Father, Son, and Holy Spirit. You may need to refine your search to get the exact verses you want. Another good resource to study this is Luther’s Small Catechism with Explanation. If you do not have access to the Catechism, you can download a pdf of it here: Luther's Small Catechism with Explanation.
Study especially the First Commandment and the Apostles’ Creed.
What do we call this God who reveals Himself as three persons? We call Him the Triune God. You won’t find the word Triune or Trinity in the Bible. But you will find proof of it. Triune simply means Three-in-One. God reveals Himself, makes Himself known to us, as the God Who is Three-in-One. How can we understand this? How can we understand that Jesus is fully human and at the same time fully God? How can we understand that Jesus’ death on the cross paid for all our sins? How can we understand that God who hates sin loves us who are full of sin? We can’t fully understand these things. But we can take God at His word. God tells us that He loves us yet hates our sin. God tells us that Jesus is the answer to our sin problem. God tells us that Jesus is fully human and also fully God. Finally, God tells us that He is one yet three: One What (God)--Three Who (Persons). He is the God who is Three-in-One.
One final verse that tells this truth is Matthew 28:18-19 (GW)18 When Jesus came near, he spoke to them. He said, “All authority in heaven and on earth has been given to me. 19 So wherever you go, make disciples of all nations: Baptize them in the name of the Father, and of the Son, and of the Holy Spirit.
Baptize in one name. Name is singular here (Jesus had perfect understanding of grammar; He knew the difference between singular and plural), yet three persons. Take God at His word. Don’t try to understand Him; just trust Him!