Albert Barnes Commentary John 14:26

"But the Comforter, [even] the Holy Spirit, whom the Father will send in my name, he shall teach you all things, and bring to your remembrance all that I said unto you." — John 14:26 (ASV)

Will send in my name. On my account. To perfect my work. To execute it as I would in applying it to human hearts. See John 14:13.

Shall teach you all things. All things which it was necessary for them to understand in the apostolic office, and particularly those things which they were not prepared then to hear or could not then understand. See John 16:12. Compare Matthew 10:19 and Matthew 10:20.

This was a full promise that they would be inspired, and that in organizing the church, and in recording the truths necessary for its edification, they would be under the infallible guidance of the Holy Ghost.

Bring all things to your remembrance. This probably refers to two things:

1. He would timely remind them of the sayings of Jesus, which they might otherwise have forgotten. In the organization of the church, and in composing the sacred history, he would preside over their memories, and recall such truths and doctrines as were necessary either for their comfort or the edification of his people. Amid the multitude of things which Jesus spoke during a ministry of more than three years, it was to be expected that many things which he had uttered, that would be important for the edification of the church, would be forgotten. We see, therefore, the nature of their inspiration. The Holy Spirit made use of their memories, and doubtless of all their natural faculties. He so presided over their memories as to recall what they had forgotten, and then it was recorded as a thing which they distinctly remembered, in the same way as we remember a thing which would have been forgotten had not some friend recalled it to our recollection.

2. The Holy Spirit would teach them the meaning of those things which the Savior had spoken. Thus they did not understand that he should be put to death until after his resurrection, though he had repeatedly told them of it (Luke 24:21, 25, 26).

   So they did not until then understand that the gospel was to be preached to the Gentiles, though this was also declared before. Compare Matthew 4:15-16 and Matthew 12:21 with Acts 10:44-48.