Midrash sa Jonas 3:8: Ein Yaakov (Glick Edition) & Shemot Rabbah

R. Ami said: "Rains are withheld solely on account of the sin of robbery; as it is said (Job 36, 32) He covereth His hands with the lightning. His hands, refers to the robbery; as it is said (Jonah 3, 8) And from the violence which is in their hands; and light, refers to rain; as it is said (Job 37, 11) He spreadeth abroad the cloud of His lightning. What is its remedy? Increasing prayer; as it is said (Ib. 36, 32) And giveth it a charge B'mafgiah; and Mafgia refers to prayer; as it is said (Jer. 7, 16) Therefore pray not thou for this people, etc., neither Tifga, (shall thou make intercession to Me)."

(Fol. 16) GEMARA: Our Rabbis were taught: If there is an aged one among them, he should address the congregation; if not, then a scholar should address them. And if there is neither then a prominent man from amongst their own should address them." Does the venerable man mentioned above refer even to one who is not a scholar? Said Abaye: "It means that if the eldest among them was also a scholar, he should address them; otherwise a scholar, even if he was younger, should address them; and if there was no scholar among them, then a prominent man should address them saying: 'Brethren! Because neither sackcloth nor fasting causes [forgiveness], but repentence and meritorious deeds; for thus we find in the case of the Ninevites. It is not written that God regarded their having wrapped themselves in sackcloth and considered their fast-days, but that God saw their works, that they had turned from their evil way.'" (Ib.) And man and beast were covered with sackcloth. What did the Ninevites do? They separated the suckling animals from their mothers and said: "Sovereign of the Universe! If Thou wilt have mercy upon us then we will have mercy upon these; but if Thou wilt not have mercy upon us, we will not have mercy upon these." (Ib.) And they called unto God with might. What does with might signify? R. Samuel maintains that they said: "Sovereign of the Universe! If one is submissive, and the other is not; if one is capable of enduring, and one is not; a righteous, and a wicked; which should yield? (Ib.) And every one turned from his evil way, and from the violence which was in their hands. What does from the violence which was in their hands signify? Samuel said: "If a man had wrongfully appropriated a beam which he had used in building a house, he tore down the house and restored the beam to its lawful owner."

“Moses said to the Lord: See, You say to me: Take this people up, but You have not informed me whom You will send with me. And You said: I know you by name and you have also found favor in My eyes” (Exodus 33:12).
“Moses said to the Lord: See, You say to me,” that is what is written: “One moment I will speak of a nation and of a kingdom, [to uproot, to smash, and to eradicate, but if that nation repents of its evil, that which I spoke of,] I will reconsider the evil [that I thought to perform against it]” (Jeremiah 18:7–8). What is, “one moment I will speak”? In the blink of an eye I decree that a person shall die, and he repents and I am reconciled with him, as it is stated: “But if that nation repents of its evil.” Who are they? These are the people of Nineveh. What is written in their regard? “Rise, go to Nineveh, the great city” (Jonah 1:2). Why? “For their wickedness has ascended before Me” (Jonah 1:2). And it says: “Jonah had begun to enter the city, a journey of one day, [and he proclaimed and said: Forty more days and Nineveh will be overturned]” (Jonah 3:4). What is written there? “The people of Nineveh believed in God, and they proclaimed a fast and they donned sackcloth” (Jonah 3:5), “man and animal” (Jonah 3:8). They said before Him: ‘Master of the universe, the animal knows nothing, and you absolve it; we, too, consider us like an animal.’ As it is stated: “Man and animal, herd and flock, shall not taste anything” (Jonah 3:7). Immediately, “God reconsidered the evil that He had said to perform against them and did not perform it” (Jonah 3:10).
The Rabbis say: “One moment I will speak of a nation,” this is Israel, as it is stated: “Who is like Your people, like Israel, a unique nation on the earth” (II Samuel 7:23). “And of a kingdom,” this is Israel, who were called a kingdom, as it is stated: “You shall be for Me a kingdom of priests” (Exodus 19:6). “To uproot, to smash, and to eradicate” (Jeremiah 1:10; 18:7); because they performed that act¹The sin of the Golden Calf. and He sought to destroy them, as it is stated: “Let Me be, and I will destroy them” (Deuteronomy 9:14). When Moses stood and asked for mercy for them, immediately, “The Lord reconsidered” (Exodus 32:14). [Moses] said before Him: ‘Master of the universe, You became full of mercy for them; lead them Yourself to ascend to the land, and not by means of an emissary.’ That is what is written: “Moses said to the Lord: See, You say to me: Take this people up.”