Jonah 3 : 1 - 5, 10

The word of the LORD came to Jonah, saying: "Set out for the great city of Nineveh, and announce to it the message that I will tell you." So Jonah made ready and went to Nineveh, according to the LORD'S bidding. Now Nineveh was an enormously large city; it took three days to go through it. Jonah began his journey through the city, and had gone but a single day's walk announcing, "Forty days more and Nineveh shall be destroyed, " when the people of Nineveh believed God; they proclaimed a fast and all of them, great and small, put on sackcloth.

When God saw by their actions how they turned from their evil way, he repented of the evil that he had threatened to do to them; he did not carry it out.