A.T. Robertson 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)

Whom (ο). Grammatical neuter, but "whom" is correct translation. The Father will send the Holy Spirit (14:16; Luke 24:49; Acts 2:33), but so will the Son (John 15:26; John 16:7) as Jesus breathes the Holy Spirit upon the disciples (20:22). There is no contradiction in this relation of the Persons in the Trinity (the Procession of the Holy Spirit). Here the Holy Spirit (full title as in Mr 3:29; Matthew 12:32; Luke 12:10) is identified with the Paraclete.

He (εκεινος). Emphatic demonstrative pronoun and masculine like παρακλητος.

Shall teach you all things (υμας διδαξε παντα). The Holy Spirit knows "the deep things of God" (1 Corinthians 2:10) and he is our Teacher in the Dispensation of the Holy Spirit of both new truth (verse 25) and old.

Bring to your remembrance (υπομνησε υμας). Future active indicative of υπομιμνησκω, old verb to remind, to recall, here only in this Gospel (cf. 3 John 1:10; 2 Timothy 2:14) and with two accusatives (person and thing). After pentecost the disciples will be able better to recall and to understand what Jesus had said (how dull they had been at times) and to be open to new revelations from God (cf. Peter at Joppa and Caesarea).