{Whom} (ho). Grammatical neuter, but "whom" is correct
translation. The Father will send the Holy Spirit ( 14:16  Lu
24:49  Ac 2:33 ), but so will the Son ( Joh 15:26  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  Mt 12:32  Lu 12:10 ) is identified
with the Paraclete. {He} (ekeinos). Emphatic demonstrative
pronoun and masculine like parakl(8874)os. {Shall teach you all
things} (humas didaxei panta). The Holy Spirit knows "the deep
things of God" ( 1Co 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} (hupomn(8873)ei humas). Future
active indicative of hupomimn(8873)k(935c), old verb to remind, to
recall, here only in this Gospel (cf.  3Jo 1:10  2Ti 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).