25 These things have I spoken unto you, being yet present with you. 26 But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you. (John 14:25-26 KJV)
William Burkitt’s Commentary
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.