Thomas Aquinas:  Secondly, charity excludes an inordinate love for evil; hence he says: it does not rejoice in wrong. For one who sins from passion commits sin with some remorse and sorrow, but one who sins from choice rejoices in the fact that he commits sin, as it says in Pr (2:14): “You rejoice in doing evil and delight in the perseverance of evil.” But charity prevents this, inasmuch as it is the love of the supreme good, to Whom all sin is obnoxious. Or he says that charity does not rejoice over evil, namely, committed by a neighbor: in fact it laments over it, inasmuch as it is opposed to our neighbor’s salvation, which it desires: “I fear that when I come again my God will humble me before you, and I may have to mourn over many of those who sinned before” (2 Cor 12:21).

William Barclay:  Love finds no pleasure in evil-doing. It might be better to translate this that love finds no pleasure in anything that is wrong. It is not so much delight in doing the wrong thing that is meant, as the malicious pleasure which comes to most of us when we hear something derogatory about someone else. It is one of the queer traits of human nature that very often we prefer to hear of the misfortune of others rather than of their good fortunes. It is much easier to weep with them that weep than to rejoice with those who rejoice. We are much more interested in hearing a spicy story to someone's discredit than a story to someone's praise. Christian love has none of that human malice which finds pleasure in ill reports.

Barnes & Murphy: Rejoiceth not in iniquity. Does not rejoice over the vices of other men; does not take delight when they are guilty of crime, or when, in any manner, they fall into sin. It does not find pleasure in hearing others accused of sin, and in having it proved that they have committed it. It does not find a malicious pleasure in the report that they have done wrong; or in following up that report, and finding it established. Wicked men often find pleasure in this, (Romans 1:32) and rejoice when others have fallen into sin, and have disgraced and ruined themselves. Men of the world often find a malignant pleasure in the report and in the evidence that a member of the church has brought dishonour on his profession. A man often rejoices when an enemy, a persecutor, or a alandeter, has committed some crime, and when he has shown an improper spirit, uttered a rash expression, or taken some step which shall involve him in ignominy. But love does none of these things. It does not desire that an enemy, a persecutor, or a slanderer should do evil, or should disgrace and ruin himself. It does not rejoice, but grieves, when a professor of religion, or an enemy of religion, when a personal friend or foe, has done anything wrong. It neither loves the wrong, nor the fact that it has been done. And perhaps there is no greater triumph of the gospel than in its enabling a man to rejoice that even his enemy and persecutor in any respect does well; or to rejoice that he is in any way honoured and respected among men. Human nature, without the gospel, manifests a different feeling; and it is only as the heart is subdued by the gospel, and filled with universal benevolence, that it is brought to rejoice when all men do well.

Joseph Beet:  Does not rejoice in unrighteousness: reveals the moral worth of love. We are not pleased at the wrong-doing of those whom we intelligently love. For we feel instinctively that by wrong-doing they injure themselves. E.g., many a bad father is sorry to see his children walking in his steps.

Brian Bell:  In Jesus interview with the woman taken in adultery, He did not condone her sin, but He protected and forgave her!

John A. Bengel:  adikia-aletheia, in iniquity-in the truth) On this antithesis see Romans 2:8.

Joseph Benson:  Love rejoiceth not in iniquity — Takes no pleasure to see an adversary fall into an error or sin, by which his reputation should be blasted, and his interest ruined. On the contrary, the man influenced by this love, is truly sorry for either the sin or folly of even an enemy; takes no pleasure in hearing or in repeating it, but desires it may be forgotten for ever.

Jeremiah Burroughs:  Erasmus tells of one who collected all the lame and defective verses in Homer's works, but passed over all that were excellent. So these, if they can spy anything defective and evil, they observe it, and gather all they can together, but will take no notice of that which is good and praiseworthy; like the kite who flies over the fair meadows and flowers, and lights only upon the carrion, or like flies that love only to be upon the sore, galled places of the horse's back.

Alan Carr:  Rejoiceth Not In Iniquity - Love does not rejoice in sin. Whether it is its own sins, or the sin of others. Love hates sin! Love does not rejoice when another falls into sin! Whether we will admit it or not, there is a part of us that is glad when another believer falls because we think it makes us look better. That is why we just have to tell someone else about it. True love does not gossip or rejoice when another believer falls, but it hurts with the injured member!

Adam Clarke:  Rejoiceth not in iniquity] ou cairei epi th adikia? Rejoiceth not in falsehood, but on the contrary, rejoiceth in the truth: this meaning adikia has in different parts of the Scriptures. At first view, this character of love seems to say but little in its favour; for who can rejoice in unrighteousness or falsity? But is it not a frequent case that persons, who have received any kind of injury, and have forborne to avenge themselves, but perhaps have left it to God; when evil falls upon the sinner do console themselves with what appears to them an evidence that God has avenged their quarrels; and do at least secretly rejoice that the man is suffering for his misdeeds? Is not this, in some sort, rejoicing in iniquity? Again: is it not common for interested persons to rejoice in the successes of an unjust and sanguinary war, in the sackage and burning of cities and towns; and is not the joy always in proportion to the slaughter that has been made of the enemy? And do these call themselves Christians? Then we may expect that Moloch and his sub-devils are not so far behind this description of Christians as to render their case utterly desperate. If such Christians can be saved, demons need not despair!

Stephen J. Cole:  Moffatt puts it, "Love is never glad when others go wrong." ... If someone you don't like falls into sin, you don't gloat; you grieve, because God is grieved over sin. ... Although love is kind and overlooks the faults of others, it does not compromise the truth or take a soft view of sin. To allow another person to go on in sin, whether it is known sin or a blind spot, is not to seek his best; it is not love. Love will sensitively confront and correct precisely because it cares deeply and knows that sin destroys.

F.C. Cook: Does not exult at the spectacle of any immoralities committed by others.

J. Cross:  Iniquity expresses unevenness or inequality — a want of rectitude or moral principle. In its largest comprehension, as here used by St. Paul, it is the great falsehood brought in by the father of lies, antagonising the goodness of the Creator, and working infinite evil to His creatures. Warring against the love of God, it tends to subvert His authority and spread disorder and anarchy throughout His empire. How, then, can charity rejoice in iniquity? Desiring the welfare of an intelligent universe, how can she rejoice in that which must result only in wretchedness and ruin?

From another Cross work:  Some are never content till they have arrested somebody's career of usefulness or honourable success, or cast a blight over some unblemished reputation, or marred the peace of stone harmonious family, or inflicted a wound upon some unsuspecting heart. For these ends they pry into your business matters, your social relations, your domestic concerns, the sacred privacy of your chambers, with a diligence worthy of the highest virtue, and an impertinence not unworthy of the lowest vice. They whisper a scandalous surmise, and enjoin the strictest secrecy, well knowing that they are giving it to every bird of the air, and sowing it broadcast on the winds of heaven. With a baseness of which Satan himself might be ashamed, they write an anonymous letter, rank with the poison of false kindness; making the postmaster an unconscious partner in their despicable enterprise, and converting the ever-welcome letter-carrier at your door into a messenger of hell. In their cowardly ambuscade they sit concealed, and by proxy play their masked batteries upon their victim, who knows not whither "to turn, nor which way to escape, nor whose the hand that wounds him. With what a fiendish satisfaction do they enjoy the mischief they have done! with what an under-chuckle of infernal glee watch the writhings of the anguish they have caused. The Comanche is more humane in his warfare; the rattlesnake is more honourable in its attack. Such a one could laugh at chains, dance in dungeons, jest over guillotines, amuse himself with inquisitorial engines, enjoy his orgies on battle-fields reeking with blood, and with his boon companions — as my own eyes have seen — make a gambling-table of his brother's grave! He could trifle at the death-bed of a Paine or a Voltaire, frolic merrily around the Saviour's Cross, and find his sweetest music in the dirge of ruined souls.

Henry Drummond:  It includes, perhaps more strictly, the self-restraint which refuses to make capital out of others' faults; the charity which delights not in exposing the weakness of others, but "covereth all things"; the sincerity of purpose which endeavors to see things as they are, and rejoices to find them better than suspicion feared or calumny denounced.

Charles Ellicott:  Rejoiceth not in iniquity.—The attitude of our mind towards sin is a great test of the truth of our religious feeling.

Joseph Exell:  "Rejoiceth not in iniquity, but rejoiceth in the truth." The best construction possible is put upon everything; on the other hand, where sin is really shown, love does not spare the sinner.

Exell & Spence:  Rejoiceth not in iniquity; rather, at unrighteousness. The rejoicing at sin, the taking pleasure in them that commit sin, the exultation over the fall of others into sin, are among the worst forms of malignity (Romans 1:32; 2 Thessalonians 2:12). The Greeks had a word, epichairekaKIa, to describe "rejoicing at the evil" (whether sin or misfortune) of others (Proverbs 24:17); Schadenfreude, "malignant joy" (Arist., 'Eth.,' 2:7, 15). It is the detestable feeling indicated by the remark of La Rochefoucald, "that there is something not altogether disagreeable to us in the misfortunes of our best friends."

Lee Gatiss: In verse 6 adikia is (unexpectedly) parallel to aletheia - the Corinthians ought not to delight in a feeling of superiority over others.

John Gill:  Rejoiceth not in iniquity -- Neither in his own, nor in others; but on the contrary is grieved for it; he mourns over his own iniquities, the corruption of his heart, the infirmities of his life, his secret sins, which none know but God and his own soul; he is greatly troubled at the profaneness and immorality of the men of the world, and the sins of professors cut him to the heart: nor does he rejoice in injustice, as the word used here may be rendered, in any unjust action or injury, that may be done to any, yea, even to an enemy; even as Christ, when Peter, in great zeal for him, drew his sword and cut off the ear of one of the high priest's servants, who was more busy than the rest in apprehending Christ, and showed more malignancy than others, was so far from rejoicing at it, that he was displeased with Peter for doing it, and was moved with so much compassion to that man, though his enemy, as to heal him.

Frédéric Louis Godet:  Finally it feels no criminal joy on seeing the faults which may be committed by men of an opposite party. Rather than eagerly turn to account the wrong which an adversary thus does to himself it mourns on account of it. This last proposition is the transition to the first of the five positive qualities which are afterwards mentioned.

John W. Gregson:  "Rejoiceth not in iniquity (chairei adikia) or is not glad when evil happens to someone, ... Those who have love in their hearts are never happy with unrighteousness or evil, for it is opposed to truth. Love does not rejoice in unrighteousness; it is never glad when others go wrong. ...

"Our sources of news tell us that the public will lap up bad and unsavory news. Christian love finds no appeal or joy in this, ..." (Sunday School Times, October 12, 1963, p. 9). There is little good news in our newspapers today; there is plenty of bad news--murders, rapes, robberies, meanness of all kinds.

F.W. Grosheide:  Injustice is falsehood for it denies rightful claims.

Guthrie & Motyer: Love does not rejoice in the opportunity to censure wrong; or, 'cannot share in the glee of the successful transgressor'.

David Guzik:  Love ... does not rejoice in iniquity: It is willing to want the best for others, and refuses to color things against others.

Matthew Henry:  It rejoiceth not in iniquity. It takes no pleasure in doing injury or hurt to any. It thinks not evil of any, without very clear proof. It wishes ill to none, much less will it hurt or wrong any, and least of all make this matter of its delight, rejoice in doing harm and mischief. Nor will it rejoice at the faults and failings of others, and triumph over them, either out of pride or ill-will, because it will set off its own excellences or gratify its spite. The sins of others are rather the grief of a charitable spirit than its sport or delight; they will touch it to the quick, and stir all its compassion, but give it no entertainment. It is the very height of malice to take pleasure in the misery of a fellow-creature. And is not falling into sin the greatest calamity that can befall one? How inconsistent is it with Christian charity, to rejoice at such fall!

Jamieson, Fausset, & Brown:  Exults not at the perpetration of iniquity (unrighteousness) by others (compare Ge 9:22, 23), ...

The false charity which compromises "the truth" by glossing over "iniquity" or unrighteousness is thus tacitly condemned (Pr 17:15).

B.W. Johnson:  Rejoiceth not in iniquity. Instead of rejoicing, is filled with sadness by wrong doing of any kind.

S. Lewis Johnson:  We have great weakness, all of us, in the fact that we often rejoice in inequity. Oh, we wouldn’t say that, but we do. We have the weakness of gloating over the sin of others. Now, we don’t come out and say that. Now, you’ve been a Christian for a little while, we know the signs of hypocrisy pretty well. So we don’t say now I’m going to gloat awhile over what’s happened to sister or brother so and so. We don’t do that. We do it in a much more professional kind of way, Christian professional kind of way. What we say is we need to pray for so and so who has done such and such. This is our way of getting around the statements of the word of God which says do not rejoice in inequity. But down deep within, rather gloating over the fact that our friend who has been provoking us in some way or another, whom we don’t like, has done something and we think we can legitimately be critical of them with reference to.

So under the cloak of sharing a need for prayer, we, in effect, gloat over our Christians. We rejoice in the evil that they have done, secretly deep down within. We don’t even want to identify. Sometimes we don’t say anything. We just have a kind of a pleased look feeling deep down within. I knew that would happen. I knew that would happen. Some of you I can tell, you are guilty. I can tell by the way your face is. You are laughing because you recognize that this is you. I recognize myself here. If I’ve been critical of something and then something happens that indicates that the person about whom I have had these doubts or questions, maybe their theology, and now they’ve done something that seems to justify my opinion, before you can catch yourself, you have gloated a little bit. I was right about that. I hope people will pay attention to me from now on.

In fact, there is a professional name for this, too. There is a good scholarly name for it because it is a German word. And you know that real scholars always have a German scholar up their sleeves that, if you get them into a corner, they pull out the German scholar who says such and such, and we cannot answer them because it’s a German scholar. Well the Germans have a word for it. They call it schadenfreude. That is the joy that we have over the difficulties of others. Put it this way, the malicious joy that we have over the misfortune of others. Everyone in this audience has been guilty of schadenfreude.

Now, let me give you some simple illustrations. It’s the joy that people have in laughing in cartoons that show people slipping on a banana peel. You ever smile at that? Of course you have. Look at you kids, you sit them in front of the TV, and they die laughing. How can you get the attention of a kid, a little kid? Prat fall. It’s just natural to the man, woman, child, infant that has the sin nature. So if you see a person buy a bag of popcorn and he trips and he loses his popcorn, what do you do? You laugh. It’s something you just cannot stop yourself from doing. You laugh. Somebody said, Ah schadenfreuder.

Well that’s precisely what takes place in the Christian life. But there is no room for schadenfreude in the Christian life. There is no room for laughing at the misfortunes that other believers have. We should be disturbed by them. They are our brothers and our sisters. And the proper response is to be concerned, truly concerned, for those who have difficulties and trials. It’s a test of our Christian love. And if we are not, then we don’t have Christian love.

William Kelly:  Hence love does not rejoice over unrighteousness, as malice does, too glad to cover its own evil by that of others.

Keith Krell:  Love does not rejoice in unrighteousness. One of the reasons I detest watching the news is that the bulk of stories concern people's misfortunes and misdeeds. There is something in our human nature which causes our attention to be drawn to murder trials, FBI probes, natural disasters, and human tragedies. Love is not like that. Love takes no joy in evil of any kind. It takes no malicious pleasure when it hears about the inadequacies, mistakes, and sins of someone else. Love is righteous. Now, after eight sobering negatives come five glorious positives.

Paul Kretzmann:  Love rejoices not at wrong, is never gratified at the evil that comes upon one's evil neighbor, nor at the fact that he persists in his evil ways.

Lange & Schaaf:  Rejoiceth not at the Iniquity,--Here, too, the thing spoken of is found outside of the subject, as may be seen from the positive antithetic clause which follows. [Jon. Edwards takes the opposite view, and understands the passage as affirming that love, so far from delighting in the practice of iniquity, tends towards holiness in the life. This is to overlook the general drift of the passage, which is rather to represent love in its relations to others]. But the iniquity to which he alludes is not iniquity in general--iniquity as it triumphs and spreads, and because it is in the ascendancy [Stanley, Wordsworth]; but, more suitably with the context, iniquity as perpetrated by particular individuals, and rebounding to their own hurt [Alford]. The trait here brought out, is that disposition to rejoice in the downfall or injury of others (Schadenfreude), which springs out of ill-will or jealousy, and which is gladdened when those who are envied for their advantages are compelled through some mis-step to come down from their high position and incur disgrace. This explanation is more natural than to suppose such a love intended as blindly or falsely approves even the errors of others, applaudit male agentibus (Grot.); comp. Romans 1:32; 12:9.

Cornelius a Lapide:  Charity does not rejoice, but grieves when it sees an enemy suffering anything wrongly or unjustly.

R.C.H. Lenski:  In fact, love has no pleasure in wrong at all: it "rejoices not over unrighteousness." In to kakon the quality of meanness in the act itself is exposed; in he adikia the quality that runs counter to the norm of divine right, God's DIke-. Thus God's verdict stands against the act; he pronounces it unrighteous. Anything that is wrong in God's sight grieves a heart that is full of love, not merely because the wrong hurts the one to whom it is done, but especially because God is displeased with the wrong and must punish the wrongdoer. Instead of rejoicing over the wrong (negative) love grieves over the wrong (positive).

Steve Lewis:  Does not rejoice in unrighteousness (chairo) = to be glad or to take pleasure in injustice or what is wrong.

J.J. Lias:  Rejoiceth not in iniquity] Cf. Psalm 5:4-5, "Thou art not a God that hath pleasure in wickedness: thou hatest all workers of iniquity." And Hosea 7:3; Romans 1:32; 2 Thessalonians 2:12.

John Lyth: 

1. IT HAS NO PLEASURE IN SIN.
   1. In the commission of it.
   2. In the contemplation of it in others.
   3. In the sufferings it occasions.