7 “For this is the love of God, that we keep His commandments.” Already you have heard, “On these two commandments hang all the law and the prophets.” See how He would not have you divide yourself over a multitude of pages: “On these two commandments hang all the law and the prophets.” On what two commandments? “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind. And, you shall love your neighbor as yourself. On these two commandments hang all the law and the prophets.” See here of what commandments this whole epis tle talks.
Therefore hold fast love, and set your minds at rest. Why do you fear lest you do evil to some man? Who does evil to the man he loves? Love: it is impossible to do this without doing good. But it may be, you rebuke. Kindness does it, not fierceness. But it may be thou beatest. For discipline you do this; because your kindness of love will not let you leave him undisciplined. And indeed there come somehow these different and contrary results, that sometimes hatred uses winning ways, and charity shows itself fierce.
A person hates his enemy, and feigns friendship for him: he sees him doing some evil, he praises him: he wishes him to go headlong, wishes him to go blind over the precipice of his lusts, haply never to return; he praises him, “For the sinner is praised in the desires of his soul;” he applies to him the unction of adulation; behold, he hates, and praises. Another sees his friend doing something of the same sort; he calls him back; if he will not hear, he uses words even of castigation, he scolds, he quarrels: there are times when it comes to this, that one must even quarrel!
Behold, hatred shows itself winningly gentle, and charity quarrels! Stay not your regard upon the words of seeming kindness, or the seeming cruelty of the rebuke; look into the vein they come from; seek the root whence they proceed. The one is gentle and bland that he may deceive, the other quarrels that he may correct. Well then, it is not for us, brethren, to enlarge your heart: obtain from God the gift to love one another. Love all men, even your enemies, not because they are your brethren, but that they may be your brethren; that you may be at all times on fire with brotherly love, whether toward him that has become your brother, or towards your enemy, so that, by being beloved, he may become your brother.
Wheresoever ye love a brother, you love a friend. Now is he with you, now is he knit to you in unity, yea catholic unity. If you are living aright, you love a brother made out of an enemy. But you love some man who has not yet believed Christ, or, if he have believed, believes as do the devils: you rebuke his vanity. Love, and that with a brotherly love: he is not yet a brother, but you love to the end he may be a brother. Well then, all our love is a brotherly love, towards Christians, towards all His members. The discipline of charity, my brethren, its strength, flowers, fruit, beauty, pleasantness, food, drink, meat, embracing, has in it no satiety. If it so delight us while in a strange land, in our own country how shall we rejoice!
Source: Homilies on the First Epistle of John (New Advent)