1 The Lord Jesus declares that He is giving His disciples a new commandment, that they should love one another. “A new commandment,” He says, “I give unto you, that you love one another.” But was not this already commanded in the ancient law of God, where it is written, “You shall love your neighbor as yourself”? Why, then, is it called a new one by the Lord, when it is proved to be so old? Is it on this account a new commandment, because He has divested us of the old, and clothed us with the new man? For it is not indeed every kind of love that renews him that listens to it, or rather yields it obedience, but that love regarding which the Lord, in order to distinguish it from all carnal affection, added, “as I have loved you.” For husbands and wives love one another, and parents and children, and all other human relationships that bind men together: to say nothing of the blame-worthy and damnable love which is mutually felt by adulterers and adulteresses, by fornicators and prostitutes, and all others who are knit together by no human relationship, but by the mischievous depravity of human life. Christ, therefore, has given us a new commandment, that we should love one another, as He also has loved us. This is the love that renews us, making us new men, heirs of the New Testament, singers of the new song. It was this love, brethren beloved, that renewed also those of olden time, who were then the righteous, the patriarchs and prophets, as it did afterwards the blessed apostles: it is it, too, that is now renewing the nations, and from among the universal race of man, which overspreads the whole world, is making and gathering together a new people, the body of the newly-married spouse of the only-begotten Son of God, of whom it is said in the Song of Songs, “Who is she that ascends, made white?” Made white indeed, because renewed; and how, but by the new commandment? Because of this, the members thereof have a mutual interest in one another; and if one member suffer, all the members suffer with it; and one member be honored, all the members rejoice with it. For this they hear and observe, “A new commandment I give unto you, that you love one another:” not as those love one another who are corrupters, nor as men love one another in a human way; but they love one another as those who are gods, and all of them sons of the Highest, and brethren, therefore, of His only Son, with that mutual love wherewith He loved them, when about to lead them on to the goal where all sufficiency should be theirs, and where their every desire should be satisfied with good things. For then there will be nothing wanting they can desire, when God will be all in all. An end like that has no end. No one dies there, where no one arrives save he that dies to this world, not that universal kind of death whereby the body is bereft of the soul; but the death of the elect, through which, even while still remaining in this mortal flesh, the heart is set on the things which are above. Of such a death it is that the apostle said, “For you are dead, and your life is hid with Christ in God.” And perhaps to this, also, do the words refer, “Love is strong as death.” For by this love it is brought about, that, while still held in the present corruptible body, we die to this world, and our life is hid with Christ in God; yea, that love itself is our death to the world, and our life with God. For if that is death when the soul quits the body, how can it be other than death when our love quits the world? Such love, therefore, is strong as death. And what is stronger than that which binds the world?
2. Think not then, my brethren, that when the Lord says, “A new commandment I give unto you, that you love one another,” there is any overlooking of that greater commandment, which requires us to love the Lord our God with all our heart, and with all our soul, and with all our mind; for along with this seeming oversight, the words “that you love one another” appear also as if they had no reference to that second commandment, which says, “You shall love your neighbor as yourself.” For “on these two commandments,” He says, “hang all the law and the prophets.” But both commandments may be found in each of these by those who have good understanding. For, on the one hand, he that loves God cannot despise His commandment to love his neighbor; and on the other, he who in a holy and spiritual way loves his neighbor, what does he love in him but God? That is the love, distinguished from all mundane love, which the Lord specially characterized, when He added, “as I have loved you.” For what was it but God that He loved in us? Not because we had Him, but in order that we might have Him; and that He may lead us on, as I said a little ago, where God is all in all. It is in this way, also, that the physician is properly said to love the sick; and what is it he loves in them but their health, which at all events he desires to recall; not their sickness, which he comes to remove? Let us, then, also so love one another, that, as far as possible, we may by the solicitude of our love be winning one another to have God within us. And this love is bestowed on us by Him who said, “As I have loved you, that you also love one another.” For this very end, therefore, did He love us, that we also should love one another; bestowing this on us by His own love to us, that we should be bound to one another in mutual love, and, united together as members by so pleasant a bond, should be the body of so mighty a Head.
3. “By this,” He adds, “Shall all men know that you are my disciples, if you have love one to another:” as if He said, Other gifts of mine are possessed in common with you by those who are not mine—not only nature, life, perception, reason, and that safety which is equally the privilege of men and beasts; but also languages, sacraments, prophecy, knowledge, faith, the bestowing of their goods upon the poor, and the giving of their body to the flames: but because destitute of charity, they only tinkle like cymbals; they are nothing, and by nothing are they profited. It is not, then, by such gifts of mine, however good, which may be alike possessed by those who are not my disciples, but “by this it is that all men shall know that you are my disciples, that you have love one to another.” O thou spouse of Christ, fair among women! O thou who ascendest in whiteness, leaning upon your Beloved! For by His light you are made dazzling to whiteness, by His assistance you are preserved from falling. How well becoming you are the words in that Song of Songs, which is, as it were, your bridal chant, “That there is love in your delights”! This it is that suffers not your soul to perish with the ungodly; it is this that judges your cause, and is strong as death, and is present in your delights. How wonderful is the character of that death, which was all but swallowed up in penal sufferings, had it not been over and above absorbed in delights! But here this discourse must now be closed; for we must make a new commencement in dealing with the words that follow.
Source: Tractates on the Gospel of John (New Advent)