When the Son prays to the Father, the Father gives also another Comforter. Viz. the Spirit of Truth, the Holy Ghost Whom the Father sends in the Name of the Son.
The Son sends the Comforter, the Spirit of Truth, Who proceeds from the Father – from the Father and to the disciples. Non-Trinitarians do not know the Father; neither do they know the Son Who sends the Comforter to the disciples.11
Regarding those three Persons (Father and Son and Spirit),12 not only does Each speak for Himself. But Each speaks also for All – and even mutually so, too. It is not in spite of but precisely because of Their distinguishable personalities, that They always have and always shall be united in essence. Genesis 1:1-3 & 1:26; Matthew 28:19; John 15:26; First John 5:6-8.