I still have many things to say to you, but you cannot bear them now. When the Spirit of truth comes, he will guide you into all the truth, for he will not speak on his own authority, but whatever he hears he will speak, and he will declare to you the things that are to come. He will glorify me, for he will take what is mine and declare it to you. All that the Father has is mine; therefore I said that he will take what is mine and declare it to you (John 16:12-15).
In verse 12, Jesus points out that there were many teachings that the disciples needed to hear, but they could not appreciate them at that time. Yet they were not to despair because the promised Spirit would soon be with them. He would be with them as the Spirit of truth, so they need not worry that somehow his presence would be less effective.
Jesus points out that the Holy Spirit will function as a guide. This means he will lead these disciples into new territory. This territory is described as ‘all truth’. Jesus does not mean that they are going to discover all geographic truth or all historical details. The range of truth is limited to his teachings. Although he was going away, he was not going to cease to be the teacher of his people. He would continue to teach them by the Holy Spirit.
The disciples needed such a guide. In the territory of ‘all truth’ they were to come across great mountains, deep valleys, wide plains and broad seas of doctrines and experiences that they would have to explain to other believers. When we think of these disciples, we must remember that they were both like us and yet different from us. They are different in the fact that they were the apostles.
As Jesus speaks to them here, he is describing a twofold activity of the Spirit. As disciples, they needed illumination by the Spirit just as we do; as apostles, they would receive inspiration from the Spirit to record infallibly the ‘all truth’ that the Spirit would teach them. This truth would be doctrines that the church should believe and practices that she should obey. Jesus is therefore revealing to these men that they would responsible for the completion of the Scriptures. The Holy Spirit would guide them and the other writers of the New Testament as they composed the various books that would be written.
Jesus then tells the disciples what will be the origin of this new revelation. He says that the Holy Spirit will not speak independently of the other members of the Trinity: ‘he will not speak on his own authority, but whatever he hears he will speak.’ This is an illustration of what each person of the Trinity speaks to the others. Within the communion of the Trinity, which is far beyond the ability of human minds to probe, there is an ongoing discussion of their eternal purpose. This is what fills their infinite minds with satisfaction and their infinite hearts with joy; every action of each person of the Trinity within the history of the universe is according to this eternal purpose.
Obviously when Jesus spoke these words, many of the future details of that purpose had not been revealed. This is why he says to the disciples that the Holy Spirit will reveal to them the things that are to come. The Holy Spirit will give them understanding concerning the future.