Jonah 3:6-10  NAS

When the word reached the king of Nineveh, he arose from his throne, laid aside his robe from him, covered himself with sackcloth and sat on ashes.  He issued a proclamation and it said, "In Nineveh by the decree of the king and his nobles; Do not let them eat or drink water.  But both man and beast must be covered with sackcloth; and let men call on God earnestly that each may turn from his wicked way and from violence which is in his hands.  Who knows, God may turn and relent and withdraw his burning anger so that we will not perish."

When God saw their deeds, that they turned from their wicked way, then God relented concerning the calamity which He had declared he would bring upon them.  And He did not do it.