1 In the Gospel lesson which precedes this one, the Lord had said: “You have not chosen me, but I have chosen you, and appointed you, that you should go and bring forth fruit, and [that] your fruit should remain; that whatsoever you shall ask of the Father in my name, He may give it you.” On these words you remember that we have already discoursed, as the Lord enabled us. But here, that is, in the succeeding lesson which you have heard read, He says: “These things I command you, that you love one another.” And thereby we are to understand that this is our fruit, of which He had said, “I have chosen you, that you should go and bring forth fruit, and [that] your fruit should remain.” And what He subjoined, “That whatsoever you shall ask of the Father in my name, He may give it you,” He will certainly give us if we love one another; seeing that this very thing He has also given us, in choosing us when we had no fruit, because we had chosen Him not; and appointing us that we should bring forth fruit—that is, that we should love one another—a fruit that we cannot have apart from Him, just as the branches can do nothing apart from the vine. Our fruit, therefore, is charity, which the apostle explains to be, “Out of a pure heart, and a good conscience, and faith unfeigned.” So love we one another, and so love we God. For it would be with no true love that we loved one another, if we loved not God. For every one loves his neighbor as himself if he loves God; and if he loves not God, he loves not himself. For on these two commandments of love hang all the law and the prophets: this is our fruit. And it is in reference, therefore, to such fruit that He gives us commandment when He says, “These things I command you, that you love one another.” In the same way also the Apostle Paul, when wishing to commend the fruit of the Spirit in opposition to the deeds of the flesh, posited this as his principle, saying, “The fruit of the Spirit is love;” and then, as if springing from and bound up in this principle, he wove the others together, which are “joy, peace, long-suffering, kindness, goodness, faith, meekness, temperance.” For who can truly rejoice who loves not good as the source of his joy? Who can have true peace, if he have it not with one whom he truly loves? Who can be long-enduring through persevering continuance in good, save through fervent love? Who can be kind, if he love not the person he is aiding? Who can be good, if he is not made so by loving? Who can be sound in the faith, without that faith which works by love? Whose meekness can be beneficial in character, if not regulated by love? And who will abstain from that which is debasing, if he love not that which dignifies? Appropriately, therefore, does the good Master so frequently commend love, as the only thing needing to be commended, without which all other good things can be of no avail, and which cannot be possessed without bringing with it those other good things that make a man truly good.
2. But alongside of this love we ought also patiently to endure the hatred of the world. For it must of necessity hate those whom it perceives recoiling from that which is loved by itself. But the Lord supplies us with special consolation from His own case, when, after saying, “These things I command you, that you love one another,” He added, “If the world hate you, know that it hated me before [it hated] you.” Why then should the member exalt itself above the head? Thou refusest to be in the body if you are unwilling to endure the hatred of the world along with the Head. “If you were of the world,” He says, “the world would love its own.” He says this, of course, of the whole Church, which, by itself, He frequently also calls by the name of the world: as when it is said, “God was in Christ, reconciling the world unto Himself.” And this also: “The Son of man came not to condemn the world, but that the world through Him might be saved.” And John says in his epistle: “We have an advocate with the Father, Jesus Christ the righteous: and He is the propitiation for our sins; and not for ours only, but also [for those] of the whole world.” The whole world then is the Church, and yet the whole world hates the Church. The world therefore hates the world, the hostile that which is reconciled, the condemned that which is saved, the polluted that which is cleansed.
3. But that world which God is in Christ reconciling unto Himself, which is saved by Christ, and has all its sins freely pardoned by Christ, has been chosen out of the world that is hostile, condemned, and defiled. For out of that mass, which has all perished in Adam, are formed the vessels of mercy, whereof that world of reconciliation is composed, that is hated by the world which belongs to the vessels of wrath that are formed out of the same mass and fitted to destruction. Finally, after saying, “If you were of the world, the world would love its own,” He immediately added, “But because you are not of the world, but I have chosen you out of the world, therefore the world hates you.” And so these men were themselves also of that world, and, that they might no longer be of it, were chosen out of it, through no merit of their own, for no good works of theirs had preceded; and not by nature, which through free-will had become totally corrupted at its source: but gratuitously, that is, of actual grace. For He who chose the world out of the world, effected for Himself, instead of finding, what He should choose: for “there is a remnant saved according to the election of grace. And if by grace,” he adds, “then is it no more of works: otherwise grace is no more grace.”
4. But if we are asked about the love which is borne to itself by that world of perdition which hates the world of redemption; we reply, it loves itself, of course, with a false love, and not with a true. And hence, it loves itself falsely, and hates itself truly. For he that loves wickedness, hates his own soul. And yet it is said to love itself, inasmuch as it loves the wickedness that makes it wicked; and, on the other hand, it is said to hate itself, inasmuch as it loves that which causes it injury. It hates, therefore, the true nature that is in it, and loves the vice: it hates what it is, as made by the goodness of God, and loves what has been wrought in it by free-will. And hence also, if we rightly understand it, we are at once forbidden and commanded to love it: thus, we are forbidden, when it is said to us, “Love not the world;” and we are commanded, when it is said to us, “Love your enemies.” These constitute the world that hates us. And therefore we are forbidden to love in it that which it loves in itself; and we are enjoined to love in it what it hates in itself, namely, the workmanship of God, and the various consolations of His goodness. For we are forbidden to love the vice that is in it, and enjoined to love the nature, while it loves the vice in itself, and hates the nature: so that we may both love and hate it in a right manner, whereas it loves and hates itself perversely.
Source: Tractates on the Gospel of John (New Advent)