So Jonah arose and went to Nineveh, according to the word of the Lord...and Jonah...cried out and said, "Yet forty days, and Nineveh shall be overthrown!"
So the people of Nineveh believe God, proclaimed a fast, and put on sackcloth, from the greatest to the least of them. Then word came to the king of Nineveh; and he arose from his throne and laid aside his robe, covered himself with sackcloth and sat in ashes. And he caused it to be proclaimed and published throughout Nineveh by the decree of the king and his nobles, saying, "Let neither man nor beast...taste anything; do not let them eat, or drink water. But let man and beast be covered with sackcloth, and cry mightily to God; yes, let every one turn from his evil way and from the violence that is in his hands. Who can tell if God will turn and relent, and turn away from His fierce anger, so that we may not perish?"
Then God saw their works, that they turned from their evil way; and God relented from the disaster that He had said He would bring upon them, and He did not do it.
From the Prophecy of St. Jonah.