16 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; 17 and behold, a voice from heaven said, “This is my beloved Son, with whom I am well pleased.”
Jesus is God. The Father is God. The Spirit is God. There is one God. This, in short, is the doctrine of the trinity. We worship the one God in three persons.
Among some believers, a belief system we call modalism has tried to redefine the doctrine of the trinity for centuries. The modalist believes that the persons of the holy trinity, the one true God, are simply different presentations of God, but not different persons. In simplest terms, these would suggest that God presented himself as the Father or Yahweh (Jehovah) in the Old Testament, but became Jesus in the New Testament. Once Jesus left, God presented as the Holy Spirit. But, to those who follow this belief system, there is no trinity, no single God who is these 3 persons all at once.
But take note of what we see happening in Matthew 3 as a simple prooftext that the doctrine of the trinity is actually biblically correct and the presentation of modalism is mistaken. At the baptism of Jesus, in one biblical picture, we see Jesus, God the Son, going into the water. We see the Spirit of God descending upon Jesus like a dove. We hear the voice of the Father. These are three persons in the frame of the picture at the very same time. There is only one God. These three persons are God. This is the trinity presented in a moment.
You might think to yourself that you have never struggled to believe in the holy trinity, even if it is hard to explain. But you might be wise to consider if you have tried to explain the trinity and ended up in a form of modalism. For example, I once heard a dear Christian attempt to illustrate the trinity by saying that a man can, at the same time, be a husband, a father, and a son. That is a perfect picture of the unbiblical doctrine of modalism. You might hear another person try to explain the trinity by reminding us that ice, water, and steam are all water. Again, this is modalism, one water changing form. Honestly, there is no such thing as a good metaphor for the trinity. We are far more likely to present false doctrine through a metaphor than we are to accurately express the infinite in a finite picture. So, I recommend we ditch any metaphor and stick with the Scripture’s claims: God the Father is God; Jesus is God; the Holy Spirit is God; There is only one God.