John 14:26 (ESV) … “But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things and bring to your remembrance all that I have said to you.”
John 14:26 is the shortest of those sections of the final discourses dealing with the Holy Spirit, yet it is probably true that it gives us the fullest definition. The Holy Spirit is described as the “Counselor.” We have already seen what this means in our discussion of verses 16–18. He is described as being “holy”—the Holy Spirit. Finally, he is described as being a “teacher.” Here are three definitions: the Counselor, Holy One, and Teacher. Yet when the verse is looked at closely, it is undoubtedly the last of these, the fact that the Holy Spirit is a teacher, that is emphasized. The role of the Holy Spirit as Counselor is emphasized in the earlier verses. The matter of holiness is emphasized in 16:7–11. But here (as also at 15:26–27 and 16:12–15) the special ministry of the Spirit as teacher is brought forward.
When the Lord says that the Holy Spirit is to “teach you all things,” the reference is primarily to the apostles. These were those whom Jesus had chosen to be authoritative spokesmen for the truth he had revealed. They were to remember it and then record it in the pages of what has become the New Testament. Moreover, this teaching was to become normative for the church. This same idea is clear in that verse in which the Lord says, “When he, the Spirit of truth, comes, he will guide you into all [the] truth.” Jesus did not mean that all that could possibly be known would be revealed to them. All things that can possibly be known are known only to God. But he did mean that the Holy Spirit would reveal to them the full truth of the gospel centered in Jesus’ life, death, and resurrection. And this he did. This was a unique ministry of the Holy Spirit to the apostles.
At the same time, however, there is a secondary sense in which these words apply to Christians who are living today. The Holy Spirit teaches us as well, and the Holy Spirit is the One who brings these things to our remembrance.[1]
[1] Boice, J. M. (2005). The Gospel of John: an expositional commentary (pp. 1147–1148). Grand Rapids, MI: Baker Books.