The New Advent page for John 15 can be found here. You can listen to the Latin here and the Greek here.
17 Hæc mando vobis: ut diligatis invicem.18 Si mundus vos odit, scitote quia me priorem vobis odio habuit. 19 Si de mundo fuissetis, mundus quod suum erat diligeret: quia vero de mundo non estis, sed ego elegi vos de mundo, propterea odit vos mundus. 20 Mementote sermonis mei, quem ego dixi vobis: non est servus major domino suo. Si me persecuti sunt, et vos persequentur; si sermonem meum servaverunt, et vestrum servabunt. 21 Sed hæc omnia facient vobis propter nomen meum: quia nesciunt eum qui misit me. 22 Si non venissem, et locutus fuissem eis, peccatum non haberent: nunc autem excusationem non habent de peccato suo. 23 Qui me odit, et Patrem meum odit. 24 Si opera non fecissem in eis quæ nemo alius fecit, peccatum non haberent: nunc autem et viderunt, et oderunt et me, et Patrem meum. 25 Sed ut adimpleatur sermo, qui in lege eorum scriptus est: Quia odio habuerunt me gratis. 26 Cum autem venerit Paraclitus, quem ego mittam vobis a Patre, Spiritum veritatis, qui a Patre procedit, ille testimonium perhibebit de me; 27 et vos testimonium perhibebitis, quia ab initio mecum estis.
The English (Douay-Rheims):
 These things I command you, that you love one another.  If the world hate you, know ye, that it hath hated me before you.  If you had been of the world, the world would love its own: but because you are not of the world, but I have chosen you out of the world, therefore the world hateth you.  Remember my word that I said to you: The servant is not greater than his master. If they have persecuted me, they will also persecute you: if they have kept my word, they will keep yours also.  But all these things they will do to you for my name' s sake: because they know not him who sent me.  If I had not come, and spoken to them, they would not have sin; but now they have no excuse for their sin.  He that hateth me, hateth my Father also.  If I had not done among them the works that no other man hath done, they would not have sin; but now they have both seen and hated both me and my Father.  But that the word may be fulfilled which is written in their law: They hated me without cause.  But when the Paraclete cometh, whom I will send you from the Father, the Spirit of truth, who proceedeth from the Father, he shall give testimony of me.  And you shall give testimony, because you are with me from the beginning.
The Catena Aurea on the injunction to love one another:
AUG. Our Lord had said, I have ordained that you should walk and bring forth fruit. Love is this fruit. Wherefore, He proceeds: These things I command you, that you love one another. Hence the Apostle said, The fruit of the Spirit is love (Gal 5:22), and enumerates all other graces as springing from this source. Well then does our Lord commend love, as if it were the only thing commanded: seeing that without it nothing can profit, with it nothing be wanting, whereby a man is made good.
CHRYS. Or thus: I have said that I lay down My life for you, and that I first chose you. I have said this not by way of reproach, but to induce you to love one another.
Then as they were about to suffer persecution and reproach, He bids them not to grieve, but rejoice on that account: If the world hates you, you know that it hated Me before it hated you: as if to say, I know it is a hard trial, but you will endure it for My sake.
AUG. For why should the members exalt themselves above the head? You refuse to be in the body, if you are not willing, with the head, to endure the hatred of the world. For love's sake let us be patient; the world must hate us, whom it sees hate whatever it loves;
If you were of the world, the world would love his own.
Can the Church ever hope to be loved by the world?
CHRYS. As if Christ's suffering were not consolation enough, He consoles them still further by telling them, the hatred of the world would be an evidence of their goodness; so that they ought rather to grieve if they were loved by the world, as that would be evidence of their wickedness.
AUG. He said this to the whole Church which is often called the world; as God was in Christ, reconciling the world to Himself (2 Cor 5:19). The whole world then is the Church, and the whole world hates the Church. The world hates the world, the world in enmity, the world reconciled, the defiled world, the changed world. Here it may be asked, If the wicked can be said to persecute the wicked; e. g., if impious kings, and judges, who persecute the righteous, punish murderers and adulterers also, how are we to understand our Lord's words, If you were of the world, the world would love his own? In this way; The world is in them who punish these offenses, and the world is In them who love them. The world then hates its own so far as it punishes the wicked, loves its own so far as it favors them. Again, if it be asked how the world loves itself, when it hates the means of its redemption, the answer is, that it loves itself with a false, not a true love, loves what hurts it; hates nature, loves vice. Wherefore we are forbidden to love what it loves in itself; commanded to love what it hates in itself. The vice in it we are forbidden, the nature in it we are commanded, to love. And to separate us from this lost world, we are chosen out of it, not by merit of our own, for we had no merits to begin with, not by nature which was radically corrupt, but by grace: But because you are not of the world, but I have chosen you out of the world, therefore the world hates you.
GREG. For the dispraise of the perverse, is our praise. There is nothing wrong in not pleasing those who do not please God. For no one can by one and the same act please God, and the enemies of God. He proves himself no friend to God, who pleases His enemy; and he whose soul is in subjection to the Truth, will have to contend with the enemies of that Truth.
AUG. Our Lord, in exhorting His servants to bear patiently the hatred of their world, proposes to them an example than which there can be no better and higher one, viz. Himself: Remember the word that I said to you, The servant is not greater than his lord. If they have persecuted Me, they will also persecute you; if they have kept My saying, they will keep yours also.
GLOSS. They observed it in order to calumniate it, as we read in the Psalms, The ungodly sees the righteousness .
The sin of rejecting Christ:
CHRYS. Thus then they have no excuse, He says; I gave them doctrine, I added miracles, which, according to Moses' law, should convince all if the doctrine itself is good also:
If l had not done among them the works that none other man did, they had not had sin.
AUG. The sin of not believing Him, notwithstanding His doctrine and His miracles. But why does He add, Which none other man did? Christ did no work greater than the raising of the dead, which we know the ancient Prophets did before Him. Is it that He did some things which no one else did? But others also did what neither He nor anyone else did. True; yet none of the ancient prophets that we read of healed so many bodily defects, sicknesses, infirmities. For to say nothing of single cases, Mark says, that wherever He entered, into villages, or cities, or country, they laid the sick in the streets, and besought Him that they might touch if it were but the border of His garment; and as many as touched Him were made whole (Mark 6:5). Such works as these no one else had done in them. In them, meaning, not amongst them, or before them, but within them. But even where particular works, like some of these, had been done before, whoever worked such did not really do them, for He did them through them, whereas He performs these miracles by His own power. For even if the Father or the Holy Spirit did them, yet it was none other than He, for the Three Persons are of one substance. For these benefits then they ought to have returned Him not hatred, but love. And this He reproaches them with But now they have both seen and hated both Me and My Father.
The coming of the Holy Ghost:
CHRYS. The disciples might say, If they have heard words from Thee, such as none other has spoken, if they have seen works of Him, such as none other has done, and yet have not been convinced, but have hated your Father, and you with Him, why do you send us to preach? How shall we be believed? Such thoughts as these He now answers: But when the Comforter is come, Whom I will send to you from the Father, even the Spirit of Truth which proceeds from the Father, he shall testify of Me.
AUG. As if He said, Seeing Me, they hated and killed Me; but the Comforter shall give such testimony concerning Me as shall make them believe, though they see Me not. And because He shall testify, you shall testify also:
And you also shall bear witness; He will inspire your hearts, and you shall proclaim with your voices. And you will preach what you know, Because you have been with Me from the beginning; which now you do not do, because you have not yet the fullness of the Spirit. But the love of God shall then be shed abroad in your hearts by the Spirit which shall be given you, and shall make you confident witnesses to Me. The Holy Spirit by His testimony made others testify, taking away fear from the friends of Christ's, and converting the hatred of His enemies into love.
DIDYMUS. The Holy Spirit He calls the Comforter, a name taken from His office, which is not only to relieve the sorrows of the faithful, but to fill them with unspeakable joy. Everlasting gladness is in those hearts, in which the Spirit dwells. The Spirit, the Comforter, is sent by the Son, not as Angels, or Prophets, or Apostles, are sent, but as the Spirit must be sent which is of one nature with the Divine wisdom and power that sends Him. The Son when sent by the Father, is not separated from Him, but abides in the Father, and the Father in Him. In the same way the Holy Spirit is not sent by the Son, and proceeds from the Father, in the sense of change of place. For as the Father's nature, being incorporeal, is not local, so neither has the Spirit of truth, Who is incorporeal also, and superior to all created things, a local nature.
CHRYS. He calls Him not the Holy Spirit, but the Spirit of truth, to show the perfect faith that was due to Him. He knew that He proceeds from the Father, for He knew all things; He knew where He Himself came from, as He says of Himself above, I know whence I came, and whither l go (John 8:14).