10 Love worketh no ill to his neighbour: therefore love is the fulfilling of the law.
[AD 407] John Chrysostom on Romans 9:22-23:24
What he means is somewhat as follows. Pharaoh was a vessel of wrath, that is, a man who by his own hard-heartedness had kindled the wrath of God. For after enjoying much long-suffering, he became no better, but remained unimproved. Wherefore he calls him not only "a vessel of wrath," but also one "fitted for destruction." That is, fully fitted indeed, but by his own proper self. For neither had God left out anything of the things likely to recover him, nor did he leave out anything of those that would ruin him, and put him beyond any forgiveness. Yet still, though God knew this, "He endured him with much long-suffering," being willing to bring him to repentance. For had He not willed this, then He would not have been thus long-suffering. But as he would not use the long-suffering in order to repentance, but fully fitted himself for wrath, He used him for the correction of others, through the punishment inflicted upon him making them better, and in this way setting forth His power. For that it is not God's wish that His power be so made known, but in another way, by His benefits, namely, and kindnesses, he had shown above in all possible ways. For if Paul does not wish to appear powerful in this way ("not that we should appear approved," he says, "but that you should do that which is honest,") [2 Corinthians 13:7], much less does God. But after that he had shown long-suffering, that He might lead to repentance, but he did not repent, He suffered him a long time, that He might display at once His goodness and His power, even if that man were not minded to gain anything from this great long-suffering. As then by punishing this man, who continued incorrigible, He showed His power, so by having pitied those who had done many sins but repented, He manifested His love toward man. But it does not say, love towards man, but glory, to show that this is especially God's glory, and for this He was above all things earnest. But in saying, "which He had afore prepared unto glory," he does not mean that all is God's doing. Since if this were so, there were nothing to hinder all men from being saved. But he is setting forth again His foreknowledge, and doing away with the difference between the Jews and the Gentiles. And on this topic again he grounds a defense of his statement, which is no small one. For it was not in the case of the Jews only that some men perished, and some were saved, but with the Gentiles also this was the case. Wherefore he does not say, all the Gentiles, but, "of the Gentiles," nor, all the Jews, but, "of the Jews." As then Pharaoh became a vessel of wrath by his own lawlessness, so did these become vessels of mercy by their own readiness to obey. For though the more part is of God, still they also have contributed themselves some little. Whence he does not say either, vessels of well-doing, or vessels of boldness (παρρησίας), but "vessels of mercy," to show that the whole is of God. For the phrase, "it is not of him that wills, nor of him that runs," even if it comes in the course of the objection, still, were it said by Paul, would create no difficulty. Because when he says, "it is not of him that wills, nor of him that runs," he does not deprive us of free-will, but shows that all is not one's own, for that it requires grace from above. For it is binding on us to will, and also to run: but to confide not in our own labors, but in the love of God toward man. And this he has expressed elsewhere. "Yet not I, but the grace which was with me." [1 Corinthians 15:10] And he well says, "Which He had afore prepared unto glory." For since they reproached them with this, that they were saved by grace, and thought to make them ashamed, he far more than sets aside this insinuation. For if the thing brought glory even to God, much more to them through whom God was glorified. But observe his forbearance, and unspeakable wisdom. For when he had it in his power to adduce, as an instance of those punished, not Pharaoh, but such of the Jews as had sinned, and so make his discourse much clearer, and show that where there were the same fathers, and the same sins, some perished, and some had mercy shown them, and persuade them not to be doubtful-minded, even if some of the Gentiles were saved, while the Jews were perishing; that he might not make his discourse irksome, the showing forth of the punishment he draws from the foreigner, so that he may not be forced to call them "vessels of wrath." But those that obtained mercy he draws from the people of the Jews. And besides, he also has spoken in a sufficient way in God's behalf, because though He knew very well that the nation was fitting itself as a vessel of destruction, still He contributed all on His part, His patience, His long-suffering, and that not merely long-suffering, but "much long-suffering;" yet still he was not minded to state it barely against the Jews. Whence then are some vessels of wrath, and some of mercy? Of their own free choice. God, however, being very good, shows the same kindness to both. For it was not those in a state of salvation only to whom He showed mercy, but also Pharaoh, as far as His part went. For of the same long-suffering, both they and he had the advantage. And if he was not saved, it was quite owing to his own will: since, as for what concerns God, he had as much done for him as they who were saved. Having then given to the question that answer which was furnished by facts, in order to give his discourse the advantage of other testimony in its favor, he introduces the prophets also making the same declarations aforetime. For Hosea, he says, of old put this in writing, as follows:

[AD 202] Irenaeus on Romans 13:10
But if He had descended from another Father, He never would have made use of the first and greatest commandment of the law; but He would undoubtedly have endeavoured by all means to bring down a greater one than this from the perfect Father, so as not to make use of that which had been given by the God of the law. And Paul in like manner declares, "Love is the fulfilling of the law: "

[AD 215] Clement of Alexandria on Romans 13:10
Whose "love worketh no ill to his neighhour".
neither injuring nor revenging ever, but, in a word, doing good to all according to the image of God. "Love is "then, "the fulfilling of the law; "

[AD 250] Fabian of Rome on Romans 13:10
And "Love worketh no ill to his neighbour."
[AD 384] Ambrosiaster on Romans 13:10
Paul is using the words of the law to arrive at the meaning of the gospel. Therefore when he records the fulfilling of the law he ties it to the gospel, demonstrating that both have a single author. Yet in the time of Christ it was necessary to add something, viz., that we should love our enemies as well as our neighbors.… What does it mean to love an enemy, except to choose not to hate him any longer and to seek to do him no harm?… For the Lord himself on the cross prayed for his enemies in order to demonstrate what the fullness of righteousness, which he had taught, actually was.

[AD 407] John Chrysostom on Romans 13:10
Observe how it has both virtues, abstinence from evils (for it "works no ill," he says), and the working of good deeds. "For it is," he says, "the fulfilling (or filling up) of the Law;" not bringing before us instruction only on moral duties in a concise form, but making the accomplishment of them easy also. For that we should become acquainted with things profitable to us was not all that he was careful for (which is the Law's care), but also with a view to the doing of them it brought us great assistance; accomplishing not some part of the commandments, but the whole sum of virtue in us. Let us then love one another, since in this way we shall also love God, Who loves us. For in the case of men, if you love a man's beloved, he that loves him is contentious at it. But here He deems you worthy to share His love, and hates you when you share not. For man's love is laden with envy and grudging; but God's is free from all passion, whence also He seeks for those to share His love. For He says, love thou with Me, and then yourself also will I love the more. You see the words of a vehement lover! If you love My beloved, then will I also reckon Myself to be greatly beloved of you. For He vehemently desires our salvation, and this He showed from of old. Now hear what He says when He was forming the man, "Let Us make man in Our Image:" and again, "Let Us make an help meet for him. It is not good for him to be alone." [Genesis 1:26] And when he had transgressed, He rebuked him, observe how gently; and He does not say, Wretch! Thou very wretch! After receiving so great benefits, have you after all trusted to the devil? And left your Benefactor, to take up with the evil spirit? But what says He? "Who told you that you are naked, unless you have eaten of the Tree, from which alone I commanded you not to eat?" [Genesis 3:11] As if a father were to say to a child, who was ordered not to touch a sword, and then disobeyed and got hurt, "How did you get hurt? By not listening to me." You see they are the words of a friend rather than a master, of a friend despised, and not even then forsaking. Let us then imitate Him, and when we rebuke, let us preserve this moderation. For even the woman He also rebukes again with the same gentleness. Or rather what He said was not so much rebuke as admonition and correction, and security against the future. This is why He says nothing to the serpent. For he was the designer of the mischiefs, and had it not in his power to put off the accusation on any one else, wherefore He punished him severely: and even here He did not come to a pause, but made the earth also to share in the curse. But if He cast them out of paradise, and condemned them to labor, even for this we ought to adore and reverence Him the most. For since self-indulgence issues in listlessness, He trenches upon the pleasure by building a fort of pain against listlessness, that we may return to the love of Him. And what of Cain's case? Does he not meet with the same gentleness? For being by him also insulted, He does not reproach (same word as insult) in return, but entreats, (or comforts) him, and says, "Why is your countenance fallen?" [Genesis 4:6] And yet what he had done allowed of no excuse whatever. And this the younger brother shows. But still even then He does not rebuke him: but what says He? "Have you sinned: keep peace;" "do so no more." "To you shall his turning be, and you shall rule over him" [Genesis 4:7, Septuagint], meaning his brother. "For if you are afraid, lest for this sacrifice," He means, "I should deprive you of the preëminence of the first-born, be of good cheer, for the entire command over him do I put into your hands. Only be thou better, and love him that has done you no wrong; for I have an interest in you both. And what makes Me most glad is, that you be not at variance one with another." For as a devoted mother, so does God do and plan everything to keep one from being torn from another; but that you may get a clearer view, by an example, of my meaning, call to your mind, pray, Rebecca in her trouble, and running about everywhere, when the elder son was at enmity with the younger. For if she loved Jacob, still she did not feel averse to Esau. And therefore she said, Lest by any means "I be deprived of both of you, my children, in one day." [Genesis 27:45] Therefore also God upon that occasion said, "You have sinned: be at peace: unto you shall his turning be" [Genesis 4:7], so repressing the murder beforehand, and aiming at the peace of them both. But when he had murdered him, He did not even then bring His care for him to a close, but again answers the fratricide in gentle terms, saying, "Where is your brother Abel?" that even now, if he would, he might make a full confession. But he struggled in defense of his former misdeeds, with a greater and sadder shamelessness. But even then God does not leave him, but again speaks the language of an iujured and despised lover, and says, "The voice of your brother's blood cries unto Me." [Genesis 4:10] And again He rebukes the earth with the murderer, turning His wrath off to it, and saying, "Cursed be the earth, which opened her mouth to receive your brother's blood" (ib. ii.); and doing like those who lament (ἀ νακαλοὕντας), as David also did when Saul was fallen. For he made an address to the mountains which received him as he died, in the words, "You mountains of Gilboa, let there fall on you neither rain nor dew, because there were the shields of the mighty cast away." [2 Samuel 1:21] And thus God also, as though singing some solitary dirge (μονῳδίαν), says, "The voice of your brother's blood cries unto Me; and now are you cursed from the earth, which has opened her mouth to receive your brother's blood from your hand." And this He said to humble his fiery passion, and to persuade him to love him at least now he had gone. Have you extinguished his life? He would say; why do you not now extinguish the hatred also? But what does He do? He loves both the one and the other, since He made them both. What then? does (4 manuscripts will) He let the murderer go unpunished? Nay, he would but have grown worse. Will He punish him then? Nay, He has more tenderness than a father. See then how He at once punishes and also displays, even in this, His love. Or rather, He does not so much as punish, but only corrects. For He does not kill him, but only fetters him with trembling, that he may divest himself of the crime, that so at least he may come back to a natural tenderness for the other, and that so at last he may make a truce with him now he has gone; for He were fain he should not go away to the other world in enmity with him that was deceased. This is the way wherein they that love, when in doing acts of kindness they meet with no love in return, are led on to be vehement and to threaten, not with their will indeed, but led by their love to do this: that at least in this way they may win over those that scorn them. Yet affection of this sort is one of compulsion, and still this even solaces them, through the vehemency of their love. And so punishment itself comes from affection, since unless pained at being hated, they would not choose to punish either. Now observe, how this is what Paul says to the Corinthians. For "who is he" (says he) "that makes me glad, but the same which is made sorry by me?" [2 Corinthians 2:2] And so when he is going to the full extent of punishment, then he shows his love. Thus the Egyptian woman too, from her vehement love, as vehemently punished Joseph: and she indeed did so for mischief, the love being unchaste; but God for good, since the love was worthy of Him who loved. This is why He does not refuse even to condescend to grosser words, and to speak the names of human passions, and to call Himself jealous. For "I am a jealous God" [Exodus 20:5], He says, that you may learn the intenseness of the love. Let us then love Him as He would have us: for He sets great store thereby. And if we turn away, He keeps inviting us, and if we will not be converted, He chastens us through His affection, not through a wish to exact punishment of us. And see what He says in Ezekiel to the city that was beloved, yet had despised Him. "I will bring your lovers against you, and will deliver you into their hands, and they shall stone you, and shall slay you, and My jealousy shall be taken away from you, and I will rest, and I will not trouble Myself any more." [From Ezekiel 16:37-42] What more than this could a vehement lover have said, when despised by his beloved, and after all again ardently loving her? For God does everything that He may be loved by us, and owing to this He spared not even His Son. But we are unbending, and savage. Yet let us become gentle at last, and love God as we ought to love Him, that we may with pleasure enjoy virtue. For if any that has a beloved wife does not perceive any of the vexations that come day by day, He that loves with this divine and pure love, only consider what great pleasure he will have to enjoy! For this is, indeed it is, the kingdom of Heaven; this is fruition of good things, and pleasure, and cheerfulness, and joy, and blessedness. Or rather, say as many things as I may, I shall still be unable to give you any such representation of it as should be, but the trial of it alone can give a knowledge of this goodly thing. Wherefore also the Prophet says, "Delight yourself in the Lord" [Psalm 37:4], and, "Taste and see that the Lord is gracious." [Psalm 34:8] Let us then be persuaded, and indulge ourselves in His love. For in this way we shall both see His Kingdom even from out of this life, and shall be living the life of Angels, and while we abide on earth, we shall be in as goodly a condition as they that dwell in heaven; and after our departing hence, shall stand the brightest of beings by the judgment-seat of Christ, and shall enjoy that glory unutterable, which may we all attain unto, by the grace and love toward man of our Lord Jesus Christ. For to Him is the glory forever, Amen.

[AD 418] Pelagius on Romans 13:10
Even not to do good is wrong. For if one sees that one’s neighbor is in danger of starvation, does one not kill him if, while one has an abundance, one does not give him food, though one has not used up one’s own provisions? For anyone who is able to help someone close to death in whatever situation of need kills that person if he does not come to his aid.

[AD 430] Augustine of Hippo on Romans 13:10
The rule of love is that one should wish his friend to have all the good things he wants to have himself and should not wish the evils to befall his friend which he wishes to avoid himself. He shows this benevolence to all men. No evil must be done to any. Love of one’s neighbor works no evil. Let us then love even our enemies as we are commanded, if we wish to be truly unconquered.

[AD 542] Caesarius of Arles on Romans 13:10
Therefore, whatever you do, do it for the love of Christ, and let the intention or end of all your actions look to him. Do nothing for the sake of human praise but everything for the love of God and the desire for eternal life. Then you will see the end of all perfection, and when you have reached it you will want nothing more.