10 And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did it not.
These things, dearly beloved, we are writing, not only to warn you but also to remind ourselves; for we are in the same arena, and the same contest lies before us. For this reason let us abandon empty and silly concerns and come to the glorious and holy rule of our tradition. Let us see what is good and pleasing and acceptable in the sight of our Maker. Let us fix our gaze on the blood of Christ and realize how precious it is to his Father, seeing that it was poured out for our salvation and brought the grace of conversion to the whole world. Let us look back over all the generations and learn that from generation to generation the Lord has given an opportunity of repentance to all who would return to him. Noah preached penance, and those who heeded were saved. Then Jonah announced destruction to the Ninevites and they repented of their sins, besought God in prayer and, estranged though they were from God, obtained salvation.
Now, if [forgiveness of sin had not] been predicted of Christ, I should find in the Creator examples of such benignity as would hold out to me the promise of similar affections also in the Son of whom he is the Father. I see how the Ninevites obtained forgiveness of their sins from the Creator—not to say from Christ [by way of anticipation], even then, because from the beginning he was acting in the Father’s name.
For the fear was the cause of their safety. The threatening effected the deliverance from the peril. The sentence of destruction put a stop to the destruction. O strange and astonishing event! The threatening of death brought forth life.
They do not know the issue, and yet they do not neglect repentance. They are unacquainted with the method of the lovingkindness of God, and they are changed amid uncertainty. They had no other Ninevites to look to, who had repented and been saved. They had not read the prophets or heard the patriarchs, or benefited by counsel, or partaken of instruction, nor had they persuaded themselves that they should altogether propitiate God by repentance. For the threat did not contain this. But they doubted and hesitated about this, and yet they repented with all carefulness. What account then shall we give, when these, who had no good hopes held out to them as to the issue, gave evidence of such a change? [What account shall you give], who may be of good cheer as to God’s love for humanity, and have many times received pledges of his care, and have heard the prophets and apostles, and have been instructed by the events themselves, and yet you do not strive to attain the same measure of virtue as they? Great then was the virtue too of these people, but much greater was the lovingkindness of God.… That fear was the parent of salvation; the threat removed the peril; the sentence of overthrow stayed the overthrow. Now they have a new and more marvelous issue! The sentence threatening death was the parent of life.… Was Nineveh destroyed? Quite the contrary. It arose and became more glorious, and all this intervening time has not effaced its glory. And we all yet celebrate it and marvel at it, that subsequently it has become a most safe harbor to all who sin, not allowing them to sink into despair but calling all to repentance, both by what it did and by what it gained from the providence of God, persuading us never to despair of our salvation.
And that these words are not a vain boast shall be made manifest to you for things that have already happened. What could be more stupid than the Ninevites? What more devoid of understanding? Yet, nevertheless, these barbarian, foolish people, who had not yet heard any one teaching them wisdom, who had never received such precepts from others, when they heard the prophet saying, “Yet three days, and Nineveh shall be overthrown,” laid aside, within three days, the whole of their evil customs. The fornicator became chaste; the bold man meek; the grasping and extortionate moderate and kind; the slothful industrious. They did not, indeed, reform one or two or three or four vices by way of remedy, but the whole of their iniquity. But where does this appear, says someone? From the words of the prophet; for the same who had been their accuser and who had said that “the cry of their wickedness has ascended up even into heaven,” himself again bears testimony of an opposite kind by saying, “God saw that every one departed from their own evil ways.” He does not say from fornication or adultery or theft, but from their “own evil ways.” And how did they depart? As God knew; not as people judged of the matter. After this are we not ashamed, must we not blush, if it turns out that in three days only the barbarians laid aside all their wickedness, but that we, who have been urged and taught during so many days, have not got the better of one bad habit? These people had moreover gone to the extreme of wickedness before; for when you hear it said, “The cry of their wickedness is come up before me,” you can understand nothing else than the excess of their wickedness. Nevertheless within three days they were capable of being transformed to a state of complete uprightness.
They applied fasting to their wounds. Yes, they even applied extreme fasting—lying prostrate on the ground, putting on sackcloth and ashes, and lamentations. More importantly, they chose a change of life. Let us then see which of these things made them whole. And how shall we know? If we come to the physician, if we seek after him earnestly, he will not hide it from us but will even eagerly disclose it. Rather, in order that no one may be ignorant or have need to ask, he has even set down in writing the medicine that restores sinners. What then is this? “God,” he said, “saw that they turned every one from his evil way, and he repented of the evil that he said he would do unto them.” He did not say simply that he saw their fasting and sackcloth and ashes, but their behavior. I say this not to question fasting (God forbid!) but to exhort you that with fasting you do that which is better than fasting, the abstaining from all evil.
"And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did it not." LXX: 'God saw their works since they turned from their wicked ways. And God repented for their wickedness that he had said he would do to them and he did not do it.' According to the two meanings of this passage God is threatening the town of Assyria and threatens the people of the world every day so that they repent: if they convert then he will change his judgement, and it will be changed by the conversion of the people. Jeremiah and Ezekiel explain this more clearly: the Lord has not fulfilled the good that he has promised to do if the good turn to sinners; nor the wickedness that he threatened the wicked if they return to safety. Thus now God sees their works, since they turn from their wicked way. But he did not hear those vain promises that Israel was in the custom of making: "all that God has said, we shall do" [Ex. 24:3.7], but he sees the works. And because he prefers a sinner's repentance rather than his death [Ez. 33:11.] he willingly changes his sentence because he has seen a change in the works. Or rather God has continued in his proposition, since he wanted to pity right from the beginning. No one in fact who desires to punish, threatens what he will actually do. The word 'wickedness' as we have noted above, can be taken to mean supplication or torture, not that God could think to do nothing on account of the wickedness.
[AD 99] Clement of Rome on Jonah 3:10