But when the Comforter is come. — Better, But when the Advocate is come. (Comp. Excursus G.)
Whom I will send unto you from the Father. — Comp. John 14:16, and Note on John 15:26. The pronoun is here emphatic. “Whom I will send...” The mission by the Father in answer to the Son’s prayer, and the mission by the Father in the Son’s name, and the mission by the Son Himself, are thought of as one and the same thing.
Even the Spirit of truth. — Comp. Note on John 14:17.
Which proceedeth from the Father. — The force of these words is to give weight to the witness which the Spirit shall bear of the Son. He is the Advocate whom the Son will send from the Father, but He is also and emphatically the Spirit of Truth proceeding from the Father, and His witness therefore will be that of the Father Himself. These two clauses (“whom I will send unto you from the Father,” “which proceedeth from the Father”) are to be regarded as parallels; and both of them probably refer to the office of the Holy Spirit. The Vulgate renders the verb in the latter clause by the word “procedit,” and the older expositors generally understood it of the person of the Holy Ghost. The Eastern Church, from the days of Theodore of Mopsuestia downwards, have claimed this text as proving the procession of the Holy Spirit from the Father only, and have quoted it as decisive against the addition of the “filioque clause” in the Nicene Creed. The Western Church, comparing it with John 16:15, and such texts as Romans 8:9; Galatians 4:6; Philippians 1:9; 1 Peter 1:11, have held that it includes the procession from the Son. If it refers to the person of the Holy Spirit, it must be granted that the ipsissima verba of our Lord are in favour of the interpretation of the Greek Church; but if it refers, as with much greater probability it does, to the office of the Holy Ghost, then these words have no bearing upon the doctrinal question at issue. The student should read on this subject, Pearson On the Creed, Art. viii., more particularly his invaluable collection of notes.
He shall testify of me. — Better, shall bear witness of Me. (Comp. Notes on John 1:7 and 1 John 5:6).