Our Lord assures them that together with their witness-bearing there will be an all-powerful witness--"the Spirit of truth"; one who could find access to the hearts and minds to which they addressed themselves and carry truth home to conviction. It was on this account that it was "expedient" that their Lord should depart, and that His visible presence should be superseded by the presence of the Spirit. It was necessary that His death, resurrection, and ascension to the right hand of the Father should take place, in order that His supremacy might be secured. And in order that He might be everywhere and inwardly present with men, it was necessary that He should be visible nowhere on earth. The inward spiritual presence depended on the bodily absence.
Before passing to the specific contents of the Spirit's testimony, as stated in vv. 8-11, it is necessary to gather up what our Lord indicates regarding the Spirit Himself and His function in the Christian dispensation. First, the Spirit here spoken of is a personal existence. Throughout all that our Lord says in this last conversation regarding the Spirit personal epithets are applied to Him, and the actions ascribed to Him are personal actions. He is to be the substitute of the most marked and influential Personality with whom the disciples had ever been brought in contact. He is to supply His vacated place. He is to be to the disciples as friendly and staunch an ally and a more constantly present and efficient teacher than Christ Himself. What as yet was not in their minds He was to impart to them; and He was to mediate and maintain communication between the absent Lord and themselves. Was it possible that the disciples should think of the Spirit otherwise than as a conscious and energetic Person when they heard Him spoken of in such words as these: "Howbeit when He, the Spirit of truth, is come, He shall guide you into all the truth: for He shall not speak from Himself; but what things soever He shall hear, these shall He speak: and He shall declare unto you the things that are to come. He shall glorify Me: for He shall take of Mine, and shall declare it unto you"? From these words it would seem as if the disciples were justified in expecting the presence and aid of One who was very closely related to their Lord, but yet distinct from Him, who could understand their state of mind and adapt Himself to them, who is not identical with the Master they are losing, and yet comes into still closer contact with them. What underlies this, and what is the very nature of the Spirit and His relation to the Father and the Son, we do not know; but our Lord chose these expressions which to our thought involve personality because this is the truest and safest form under which we can now conceive of the Spirit.
The function for the discharge of which this Spirit is necessary is the "glorification" of Christ. Without Him the manifestation of Christ will be lost. He is needed to secure that the world be brought into contact with Christ, and that men recognise and use Him. This is the most general and comprehensive aspect of the Spirit's work: "He shall glorify Me" (ver. 14). In making this announcement our Lord assumes that position of commanding importance with which this Gospel has made us familiar. The Divine Spirit is to be sent forth, and the direct object of His mission is the glorifying of Christ. The meaning of Christ's manifestation is the essential thing for men to understand. In manifesting Himself He has revealed the Father. He has in His own person shown what a Divine nature is; and therefore in order to His glorification all that is required is that light be shed upon what He has done and been, and that the eyes of men be opened to see Him and His work. The recognition of Christ and of God in Him is the blessedness of the human race; and to bring this about is the function of the Spirit. As Jesus Himself had constantly presented Himself as the revealer of the Father and as speaking His words, so, in "a rivalry of Divine humility," the Spirit glorifies the Son and speaks "what He shall hear."