The Theologian Fred Sanders explains in his book, How the Trinity Changes everything, this important aspect of Biblical interpretation;
“One of the most powerful features of the Trinitarianism of the New Testament is that it is revealed to us largely in the conversation between the Father and the Son.…Even in the darkness of the cross itself, the Son keeps up an intimate running dialogue with his Father. Jesus is confident that his prayers are heard and that the Father is with him, and in a few spectacular instances of a voice speaking from heaven we get to hear the Father declaring his attitude toward his beloved Son. All this inner-Trinitarian conversation is intentionally held in public, for our instruction….what they said to and about one another for us to overhear is not only a solid foundation for the doctrine of the Trinity, but it is also a marvelous invitation to us to be included in that conversation.”
We see this dialogue at Christ’s baptism and at the transfiguration. We hear it in the prayer of Jesus at Lazarus’ tomb:
John 11:41–42, So they took away the stone. And Jesus lifted up his eyes and said, “Father, I thank you that you have heard me. I knew that you always hear me, but I said this on account of the people standing around, that they may believe that you sent me.”
Jesus is talking to the Father, out loud, so that others may hear and join in the knowledge of the Father and the Son.
This is why the disciples ask Jesus to teach them to pray in Luke 11:1. The dialogue between Jesus and His Father is public and meant to draw us in.
So we turn to John 19:28–29 After this, Jesus, knowing that all was now finished, said (to fulfill the Scripture), “I thirst.” A jar full of sour wine stood there, so they put a sponge full of the sour wine on a hyssop branch and held it to his mouth.
What we think is happening here is strictly an exchange between Jesus and His murderers.
Indeed, Jesus is fulfilling the scriptures, like Psalm 22:15 my strength is dried up like a potsherd, and my tongue sticks to my jaws.
But in this moment when Jesus speaks of thirst, as in His whole earthly ministry, He is misunderstood by His immediate audience.
Understanding what is being said, to whom and its meaning – is an invitation for us to join the inner life of the trinity.