John 16:13-15
“He shall not speak of Himself; but whatsoever He shall hear, that shall He speak; and He will show you things to come. He shall glorify Me; for He shall receive of Mine, and shall show it unto you. All things that the Father has are Mine.”
For since He had told them, that “'He shall teach you, and bring to your remembrance', and shall comfort you in your afflictions,” (which He Himself did not,) and that “it is expedient for you that I should depart”, and that He should come, and, “'now you are not able to bear', but then ye shall be able,” and, that “He shall lead you into all truth”; lest hearing these things they should suppose the Spirit to be the greater, and so fall into an extreme opinion of impiety, therefore He says, “He shall receive of Mine,” that is, “whatsoever things I have told you, He shall also tell you.” When He says, “He shall speak nothing of Himself,” He means, “nothing contrary, nothing of His own opposed to My words.” As then in saying respecting Himself, “I speak not of Myself”, He means that He speaks nothing beside what the Father says, nothing of His own against Him, or differing from Him, so also with respect to the Spirit. But the, “of Mine,” means, “of what I know,” “of My own knowledge”; “for the knowledge of Me and of the Spirit is one.”
“And He will tell you things to come.” He excited their minds, for the race of man is for nothing so greedy, as for learning the future. This, for instance, they continually asked Him, “Where are you going?” “Which is the way?” To free them therefore from this anxiety, He says, “He shall foretell you all things, so that you shall not meet with them without warning.”
“He shall glorify Me.” How? “In My name He shall grant His inward workings.” For since at the coming of the Spirit they were about to do greater miracles, therefore, again introducing the Equality of Honor, He says, “He shall glorify Me.”
What means He by, “all truth”? For this also He testifies of Him, that “He shall guide us into all truth.” Because He was clothed with the flesh, and because He would not seem to speak concerning Himself, and because they did not yet know clearly concerning the Resurrection, and were too imperfect, and also because of the Jews, that they might not think they were punishing Him as a transgressor; therefore He spoke no great thing continually, nor plainly drew them away from the Law. But when the disciples were cut off from them, and were for the future without; and when many were about to believe, and to be released from their sins; and when there were others who spoke of Him, He with good reason spoke not great things concerning Himself. “So that it proceeded not from ignorance of Mine,” He says, “that I told you not what I should have told you, but from the infirmity of the hearers.” On this account having said, “He shall lead you into all truth,” He added, “He shall not speak of Himself.” For to show that the Spirit needs not teaching, hear Paul saying, “So also the things of God knows no man, but the Spirit of God.” “As then the spirit of man, not learning from another, knows; so also the Holy Spirit 'shall receive of Mine,'” that is, “shall speak in unison with what is Mine.”
“All things that the Father has are Mine.” “Since then those things are Mine, and He shall speak from the things of the Father, He shall speak from Mine.”
3. “But why did not the Spirit come before He departed?” Because the curse not having yet been taken away, sin not yet loosed, but all being yet subject to vengeance, He could not come. “It is necessary then,” says He, “that the enmity be put away, that we be reconciled to God, and then receive that Gift.” But why says He, “I will send Him”? It means, “I will prepare you beforehand to receive Him.” For, how can that which Is everywhere, be “sent”? Besides, He also shows the distinction of the Persons. On these two accounts He thus speaks; and also, since they were hardly to be drawn away from Himself, exhorting them to hold fast to the Spirit, and in order that they might cherish It. For He Himself was able to have wrought these things, but He concedes to the Spirit the working of miracles, on this account, that they might understand His dignity. For as the Father could have brought into being things which are, yet the Son did so, that we might understand His power, so also is it in this case. On this account He Himself was made Flesh, reserving the inward working for the Spirit, shutting up the mouths of those who take the argument of His ineffable love for an occasion of impiety. For when they say that the Son was made flesh because He was inferior to the Father, we will reply to them, “what then will you say of the Spirit?” He took not the flesh, and yet certainly on this account ye will not call Him greater than the Son, nor the Son inferior to Him. Therefore, in the case of baptism also the Trinity is included. The Father is able to effect the whole, as is the Son, and the Holy Ghost; yet, since concerning the Father no man doubts, but the doubt was concerning the Son, and the Holy Ghost, They are included in the rite, that by Their community in supplying those unspeakable blessings, we may also fully learn Their community in dignity. For that both the Son is able by Himself to do that which in the case of baptism He is able to do with the Father, and the Holy Ghost the same, hear these things said plainly. For to the Jews He said, “That ye may know that the Son of Man has power on earth to forgive sins”; and again, “That ye may become children of light”: and, “I give to them eternal life.” Then after this, “That they might have life, and might have it more abundantly.” Now let us see the Spirit also performing the same thing. Where can we see it? “But the manifestation of the Spirit,” it says, “is given to every man to profit withal”; He then that gives these things, much more remits sins. And again, “It is the Spirit that quickens”; and, “Shall quicken you by His Spirit which dwells in you”; and, “The Spirit is Life because of righteousness”; and, “If you are led by the Spirit, you are not under the Law.” “For you have not received the Spirit of bondage again to fear, but you have received the Spirit of adoption.” All the wonders too which they then wrought, they wrought at the coming of the Spirit. And Paul writing to the Corinthians, said, “But you have been washed, but you have been sanctified in the name of our Lord Jesus Christ, and by the Spirit of our God.” Since then they had heard many things of the Father, and had seen the Son work many things, but as yet knew nothing clearly of the Spirit, that Spirit does miracles, and brings in the perfect knowledge. But (as I said before) that He may not thence be supposed to be greater, on this account Christ says, “Whatsoever He shall hear, that shall He speak; and He will show you things to come.” Since, if this be not so, how could it be otherwise than absurd, if He was about to hear then, and on account of those who were being made disciples? For according to you, He would not even then know, except on account of those who were about to hear. What could be more unlawful than this saying? Besides, what would He have to hear? Did He not speak all these things by the Prophets? For if He was about to teach concerning the dissolution of the Law, it had been spoken of: if concerning Christ, His Divinity and the Dispensation, these had been spoken of also. What could He say more clearly after this?
Source: Homilies on the Gospel of John (New Advent)