I. The Holy Spirit is promised as another Comforter. This surely indicates, not a new office to be discharged, but an old one, or one already subsisting, to be discharged by a new person. The term "Comforter" is common to the Holy Ghost, and to the incarnate Son. In its highest and holiest import, it is clearly not the exclusive property of the Spirit. The ministry is the same though another minister is to be employed in it. The work is the same, though a new and different workman is to be engaged about it. "I will pray the Father, and He shall give you another Comforter."
II. And for that office of Comforter or Advocate, the Holy Spirit is better fitted, at least for the present, than even the Lord Jesus in person, had He remained on earth, could have been. (1) The other Comforter or Advocate is to be no passing visitor merely, but a permanent resident here on earth, "He may abide with you for ever." His peculiar functions, the department of the work falling to Him, is not of such a sort as to limit the duration of His stay or sojourn here. On the contrary, it requires His unceasing and uninterrupted ministry always, from the beginning of the Gospel down to the end of time. (2) He is the Spirit of Truth. In that character and capacity, He spiritualises the truth; making it spirit and life. In the hands of any other, even of Christ, the truth, the highest truth, the truth Divine and heavenly, the truth consisting of the very Son Himself, His person and His work, is but flesh which profiteth nothing. The Lord's own personal teaching, had it been prolonged, would have lacked a certain element of living and life-giving energy a certain vitality and vivifying force, which it can only have when the Spirit makes it His own impregnates it with His own life, and assimilates it in some sense, to His own nature. (3) The Spirit is an agent or worker, such as the world does not see or know, and therefore cannot receive. Were He other than that, He would not meet your case; He might dwell with you, but He could not be in you. "It is expedient for you that I go away," for this among other reasons, that He whom I am to send can reach the inmost recesses of your inner man and fix My words deeply there. "He dwelleth with you, and shall be in you."
R. S. Candlish, Sonship and Brotherhood of Believers,p. 192.
References: John 14:16-26. Preacher's Monthly,vol. vii., p, 336. John 14:17. W. Sanday, The Fourth Gospel,p. 221; Spurgeon, Sermons,vol. xiii., No. 754; Preacher's Monthly,vol. ix., p. 280; R. Tuck, Christian World Pulpit,vol. xxiii., p. 381. Joh 14:18. Wilberforce, Church Sermons,vol. ii., p. 17; G. Moberly, Plain Sermons at Brightstone,p. 219; Christian World Pulpit,vol. i., p. 401; Homiletic Quarterly,vol. i., p. 199. John 14:18; John 14:19. J. H. Newman, Sermons on Subjects of the Day,p. 137. John 14:18-20. G. Moberly, Parochial Sermons,p. 145; W. Roberts, Christian World Pulpit,vol. x., p. 56; J. Vaughan, Sermons,13th series, p. 165.