The Trinity is one of the most foundational doctrines of Christianity and yet one of the hardest. It seems to involve a paradox: one God, three Persons. How can that be? How do we escape tritheism without nullifying the divinity of Christ and the Holy Spirit?
The paradox is ancient. The Early Christians had many heretics who professed doctrines which either avowed tritheism or stole deity from the Second and Third persons of the Trinity. Even before the Early Christians, Neo-Platonists had grappled with the philosophical problem of The One and The Many… How can human beings, who are many, have a portion of the Divine Mind, which is only One? Plotinus and others proposed all kinds of strange solutions which you can see in Hinduism, Buddhism, Monism, and New Age today.
And yet, the Trinity is woven throughout Scripture. It is first hinted at in the OT and then more specifically revealed in the NT.
There are great websites that give all the Scriptures for proof of the Trinity and go into the nature (role) of the Holy Spirit, who is probably least understood. So I will not go into all that here. I’ll just say that in the OT, the Trinity can be put together empirically but it is not altogether obvious because of the limited yet progressive revelation of who God is. He is not “Father” yet, and revelation of who He is is increasingly needed by the post-Babel era. By the time Moses is delivering the Israelites, he seems to be introducing Yahweh all over again to the common man. With this in mind, we have to take the clues wherever we can find them. The first clue, however, is fortunately found in Genesis 1 where God is creating but so is the Spirit hovering over the waters. Clearly two separate agents. If you add in the NT counsel on the subject, Jesus was actually the Living Word that mediated the heavenly becoming physical in the beginning (John 1). We already know that before the foundation of the world, Jesus was slain. And that all things were made “by Him and for Him.” So clearly His agency is present at Genesis as well.
Assuming that you don’t need proof of the Father’s persona in the OT, other appearances of the Holy Spirit’s divinity and separate agency in OT include each time that “the Spirit” comes upon someone. The Spirit falls on Saul, causing him to prophesy so that everyone asks if he is among the Prophets. The Spirit falls on Samson, causing him to knock down the Philistine’s temple. The Spirit fills Isaiah’s mouth when he is burned by the coal, to prophesy. And Ezekiel acknowledges the Spirit’s filling when he sees his visions. These are all explicit mentions in the Scripture of the Spirit. Other implicit mentions are David’s psalm and worship, Solomon’s supreme wisdom, and the prophecies of the other Major and Minor Prophets.
So where, you ask, is Jesus? While Jews refuse to acknowledge Jesus as Messiah, the truth is that from a NT perspective, you can see Jesus throughout the OT. Remember that Jesus Himself walked with the disciples from Emmaus and told them where He could be found in the Scriptures (which were only OT Scriptures at that time, no NT yet!). So if Jesus found Himself there, we know He is there. Specifically, Jesus might have pointed out His being the fourth man in the fiery furnace with Daniel and his friends. He might have said He was the angel Jacob wrestled with who blessed Him. He might have said He was the commander of the army who came to Joshua and asked him to fight on the Lord’s side. He certainly was the suffering servant described by Isaiah.
So it is clear that these Three Persons of the Trinity do show up in the OT if you look carefully. It isn’t eisegeting the text, it is actually making sense of it. A great example of this is David’s psalm which begins, “The Lord said to my Lord, “Sit at my right hand until I put your enemies under your feet.” How is one to interpret this unless there is counsel in the Godhead? (see Mark 2:35-37 where Jesus interprets this passage.) More importantly, the Trinity is alluded to in one of the most foundational Jewish Scriptures, the Shm’ah… “Hear O Israel, the Lord your God is one.” While the verse professes God is one, the word for “God” is Elohim, which is plural. So in some sense it reads, “Hear O Israel, the Lord (singular) your Gods (plural) is One.” Interesting contradiction right in the Scripture, right? And this is no hand-waving verse.
When you get to the NT, the examples are more noticeable. First of all, Jesus is clearly on earth doing the will of His Father in heaven. He communes with Him, prays to Him, and confesses to Him all while He is ministering so we know the Father and Jesus are two separate agents coexisting at the same time. Moreover, God is clear that He has given all authority to His son, which is why we worship Him alone and confess He is Lord. So from the Father’s own mouth, we know Jesus is divine.
There are also several instances where Jesus and the Holy Spirit are seen together as agents, such as when Jesus blows on His disciples and says, Receive Ye the Holy Spirit. Also when the Holy Spirit impregnates Mary, begetting Jesus (Luke 1:30). And when Jesus was led into the wilderness by the Spirit to be tempted of the devil. But perhaps one of the most startling acknowledgments of the Spirit’s divinity and personhood is Jesus’ warning that those who blaspheme Him will be forgiven but those who blaspheme the Holy Spirit will not (Luke 12:8).
Some instances acknowledge the pair of the Father and the Spirit, such as when the disciples are praying in the upper room (to the Father) and the Holy Spirit in response fills their room with the wind and tongues of fire. Another acknowledgment is where Jesus tells us that the Father gives good gifts and will give us the Holy Spirit if we ask Him. This is important because it specifically says the origin of the Holy Spirit is the Father himself. The Spirit is therefore both divine and separate (something He can give). There are other Scriptures where the Spirit falls, fills, or is given, proving this statement.
But several instances in the NT make all three divine agents clear… such as Jesus’ baptism. When Jesus is submerged in the Jordan by John the Baptist, heaven is opened and the Father’s voice is heard. Then the Spirit is visibly seen in the form of a dove descening from heaven down upon Jesus. Very clearly three divine agents all at the same moment, witnessed by onlookers. Another moment is where Jesus explains that it is better that He go so another may come. He says, “When the Counselor comes, whom I will send to you from the Father, the Spirit of truth who goes out from the Father, he will testify about me (John 15.26).” The agency of Jesus, the Father, and the Spirit is very distinct, very divine, and very personal. But perhaps the most prominent verse of Scripture that acknowledges the Trinity is the Great Commission where we are told to baptize in the name (singular) of the Father, the Son, and the Holy Spirit. This is like the Christian’s Shm’ah… no handwaving Scripture.
Besides compelling Scripture verses and narratives, there are structural reasons why Christianity reflects the Trinity. By structural, I mean aspects that are built into the way God sovereignly decided to design the universe. we don’t know why, He just did it that way.
For example, OT law makes it clear that three witnesses are God’s style. A cord of three strands cannot be broken (Ecclesiastes 4:12). Three ancestors populate the post-Flood world. Three angels visit Abraham to tell him he will have a son. Three festivals are commanded by Moses for the Lord to meet with all the people, three times a year. Three cities are established as places of refuge. Two lampstands bear witness of the Lord’s presence (the third witness) outside the Temple. Three men are thrown into the fiery furnace. The NT corroborates by saying by the mouths of two or three witnesses will a matter be established (Matthew 18:16; 1 Timothy 5:19). Three wise men establish Jesus’ birth to the Gentile world. Three disciples witness Jesus’ transfiguration. Two witnesses testify of the Lord (the third witness) in the Last Days. There is something about the triune nature of witnesses to an event that God has sovereignly decided will be built into the structure of the universe… probably as an apologetic that He actually exists and will verify His will to be done. In other words, there are “legal” reasons why God develops a Trinity… before the world, there were no human witnesses, but the Holy Spirit and Jesus were with God before the foundations of the world and witnessed His will. So by the “mouth” of Three Witnesses, the ultimate Matters were established.
Not only did the Trinity witness creation, but they actually counseled it. Jesus and the Holy Spirit were present at creation, participating and counseling with the Father. This is important because the entire basis of Christianity is the understanding that we are being reconciled to God to participate with Him and His Kingdom. Our part (in Christ) is analogous to His part in the beginning; we are supposed to be creating His Kingdom (in a second-hand sense) and counseling with Him, receiving Him like a Father. The relational aspect of the Trinity then is the way we know it is ok (even God’s will) to have a relationship with the Father. Indeed, the relational worldview of Christians– to God and others– is probably the defining characteristic that separates Christianity from all other religions in the world.
Another “legal” thing written into God’s design is the idea of covenant. God’s covenants with His people were always in three parts: the words (promises, terms); the blood (sacrifice); and the seal (assurance). Every time covenantal language comes up in the Old Testament–Adam and Eve, Noah, Abraham, Moses, Joshua, David–there are the words, the blood, and the seal. Three things. And by the time we get to Jesus and His new covenant, it is still evident: the Father’s words/terms (promise of eternal life, our confession that Jesus is Lord and risen from the dead); His blood (spilled on the cross); and the seal of the Holy Spirit. The Trinity in action. The Trinity, in essence, makes the covenant work.