William Burkitt on John 14:25

Here we have a repeated promise of the mission of the Holy Ghost, called The Comforter, and his special office declared; namely, to teach, and to bring to remembrance what Christ had taught; He shall teach you all things. As the Spirit of God is the great Comforter, so he is the Special Teacher, of his children; he teacheth condescendingly, stooping to the meanest capacities; he teacheth efficaciously, inclinging the heart to receive instruction, as well as opening the ear to hear it: he teacheth plainly and clearly, unerringly and infallibly; he is truth itself, and therefore his teachings are most true.

And as the Holy Spirit is the saint's Teacher, so is he also their Remembrancer: He shall bring all things to your remembrance; that is, all truths needful to be known, and necessary to salvation.

Here note, That the Holy Spirit teaches nothing but what Christ himself taught; the Spirit teaches in the word, and by the word, but never teaches any thing contrary to the word: He shall teach and bring to remembrance whatsoever I have said unto you.