“All this I have spoken while still with you. But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you.” – John 14:25-26
“I have much more to say to you, more than you can now bear. But when he, the Spirit of truth, comes, he will guide you into all the truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come. He will glorify me because it is from me that he will receive what he will make known to you. All that belongs to the Father is mine. That is why I said the Spirit will receive from me what he will make known to you.” – John 16:12-15
These verses foretell the writing of the New Testament. Jesus is teaching His disciples as He prepares to go to the cross and says that the Holy Spirit “will remind you of everything I have said to you.” He also says that He has “much more to say to you, more than you can now bear.” Jesus promises both the writing of the gospels through the Spirit reminding them of all that Jesus taught, as well as the rest of the New Testament as the Spirit guides them into all truth.
Later, after the Resurrection, Jesus tells them to wait in the city until the Holy Spirit comes.
“I am going to send you what my Father has promised; but stay in the city until you have been clothed with power from on high.” – Luke 24:49
This is fulfilled in Acts 2 on the day of Pentecost when,
“Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them.” – Acts 2:2-4
This is the beginning of the fulfillment of what Jesus spoke about when He said, “the Spirit will receive from me what he will make known to you.” Through the indwelling of the Holy Spirit, Jesus was able to teach the disciples–and consequently us–those things that were “too much to bear”.
Carried along by the Holy Spirit (2 Peter 1:21) the writers of the New Testament recorded the words of God (2 Timothy 3:16). From John 1 we know that Jesus is the Word and through the Spirit (John 15:15) Jesus directed the teaching and writing of the New Testament.
Going back to Jesus as He is teaching the disciples before He goes to the cross, in essence He is telling them, this isn’t over, there is more coming. I am about to die, but that is not the end, far from it. Acts opens with the great line,
“In my former book, Theophilus, I wrote about all that Jesus began to do and to teach until the day he was taken up to heaven, after giving instructions through the Holy Spirit to the apostles he had chosen.” – Acts 1:1-2
The gospels contain what Jesus “began to do and to teach“. The teachings of Christ are throughout scripture, not just contained in the “red letter” verses. His work securing our salvation was complete (Hebrews 10:12), but His revelation of that work continued. When we are reading the Bible, say for example Colossians, we are reading the teaching of Jesus through the Holy Spirit inspiring and using Paul as he writes. Through the Holy Spirit and the Word Jesus is teaching us still today.