2 Corinthians 12:21

For in saying, toward the end of the Epistle, "Lest, when I shall have come, God humble me, and I bewail many of those who have formerly sinned, and have not repented of the impurity which they have committed, the fornication, and the vileness," he did not, of course, determine that they were to be received hack (by him into the Church) if they should have entered (the path of) repentance, whom he was to find in the Church, but that they were to be bewailed, and indubitably ejected, that they might lose (the benefit of) repentance.

And yet to these persons themselves repentance is granted, and the hope of lamenting and atoning is left, according to the saying of the same apostle: "I fear lest, when I come to you, I shall bewail many of those who have sinned already, and have not repented of the uncleanness, and fornication, and lasciviousness which they have committed.".
Also in the same: "But I fear lest perchance, when I come to you, God may again humble me among you, and I shall bewail many of those who have sinned before, and have not repented, for that they have committed fornication and lasciviousness."

Paul is saying that some have repented but others have not. This contradicts Novatian, who claims that fornicators cannot repent or be received back into communion. Paul is affirming that they have indeed repented, and because of this they have been received back into the peace of the church.

"And lest when I come again, my God should humble me among you."

And the word "again," too, is as smiting them. For he means, 'What happened before is enough;' as he said also in the beginning [of the Epistle], "to spare you, I came not as yet to Corinth." Seest thou how he shows both indignation and tender affection? But what means, "will humble me?" And yet this is glorious rather, to accuse, to take vengeance, to call to account, to be seated in the place of judge; howbeit he calls it a humbling. So far was he from being ashamed of that [cause of] humbling, because, "his bodily presence was weak, and his speech of no account," that he wished to be even for ever in that case, and deprecated the contrary. And he says this more clearly as he proceeds; and he counts this to be especially humbling, to be involved in such a necessity as the present, of punishing and taking vengeance. And wherefore did he not say, 'lest when I come I shall be humbled,' but, "lest when I come my God will humble me." 'Because had it not been for His sake, I should have paid no attention nor been anxious. For it is not as possessing authority and for my own pleasure, that I demand satisfaction, but because of His commandment.' Now above, indeed, he expressed himself thus, "I shall be found;" here, however, he relaxes and adopts milder and gentler language, saying,

"I shall mourn for many of them who have sinned." Not simply, "who have sinned," but,

"Who have not repented." And he said not, 'all,' but "many;" nor made it clear who these were either, thereby making the return unto repentance easy to them; and to make it plain that a repentance is able to right transgressions, he bewails those that repent not, those who are incurably diseased, those who continue in their wounds. Observe then Apostolic virtue, in that, conscious of no evil in himself, he laments over the evils of others and is humbled for other men's transgressions. For this is the especial mark of a teacher, so to sympathize with the calamities of his disciples, and to mourn over the wounds of those who are under him. Then he mentions also the specific sin.

"Of the lasciviousness and uncleanness which they committed." Now in these words he alludes indeed to fornication; but if one carefully examine the subject, every kind of sin can be called by this name. For although the fornicator and adulterer is preeminently styled unclean, yet still the other sins also produce uncleanness in the soul. And therefore it is that Christ also calls the Jews unclean, not charging them with fornication only, but with wickedness of other kinds as well. Wherefore also He says that they made the outside clean, and that "not the things which enter in defile the man, but those which come out from him;" and it is said in another place, "Every one that is proud in heart is unclean before the Lord."

Concerning those who though within the church persisted in their evil deeds, he spoke thus to the Corinthians with these words of comfort: "I fear that when I come again, my God may humiliate me before you, and I may have to mourn over many of those who sinned earlier and have not repented of the impurity, immorality and licentiousness they practiced." The apostle would not be saddened or humiliated in mourning over them if he believed that the forgiveness of sins would be granted to sinners and the wicked who continue to exasperate the divine justice without conversion of heart. The forgiveness of sins has no effect except in the conversion of the heart. We refer to those who have been converted by divine aid through the exercise of their own freedom of choice and whose lives are genuinely changed for the better. These converts will still occasionally sin, either through ignorance or through the stubbornness of a will that is knowingly lured by evil. They do not, however, stop asking for the forgiveness of their sins.

That is, the above said is sufficient, and I am afraid that, having come to you, I will be compelled to deal with you severely. By humiliation, then, he means the necessity of strongly punishing someone, although many consider this an honor for themselves. And he did not say "lest I be humiliated," but "lest my God humiliate me," showing that he would do this for the sake of God. And if the matter did not concern God and His commandments, he himself would not have appeared so severe. By the words "my God" he shows his fervent love for God.

Notice the tenderness of the apostle: he bewails the transgressions of others. He did not say "all," but "many," and not simply "who have sinned," but also "have not repented," because those who persist in their wound are worthy of compassion. He also does not expose them, giving them a convenient path to repentance; for he mentioned repentance so that they might turn to it, and so that when he comes, he would not have to punish them and therefore be humbled, that is, grieve exceedingly. Notice also that he mentioned repentance on account of the Novatians. By sin, understand every kind of uncleanness, because every sin defiles. Or in particular, the abominations of carnal intercourse, for in Corinth there was not just one adulterer, but many, and moreover in many forms of licentiousness.

Then he manifests their wickedness in regard to past evils for which they have not repented, when he says: I fear that when I come again my God may humble me, i.e., afflict me, before you and I may have to mourn over many of those who sinned before, i.e., before the first epistle. And rightly do I mourn, because just as the glory of the father is in the glory of his children, so the father's shame is the shame of the children. Thus did Samuel mourn over Saul: "How long will you grieve over Saul, seeing I have rejected him from being king over Israel?" (1 Sam. 16:1). And this because they have not repented or done penance for their past carnal sins, some of which are contrary to nature; hence he says, and have not repented of the impurity, i.e., lust contrary to nature. Some are committed with women no longer virgins, namely, widows or married women; hence he says, immorality [fornication]; others are committed by deflowering virgins; hence he says, and licentiousness which they have practiced continually: "Now the works of the flesh are plain: fornication, impurity, licentiousness" (Gal. 5:19).