God saw their works, that they turned from their evil way. God repented of the evil which he said he would do to them, and he didn't do it.
Some have complained that there is no archeological or documentary testimony regarding this wholesale repentance in Nineveh, but no thoughtful person could really be surprised by that.  "It is very unusual in monumental history to find mention of any events except wars and the execution of material works."[39] Those who allege that "There is no ancient documentary proof of the great repentance in Nineveh," are profoundly mistaken.  There is documentation of it in the Gospel of Matthew; and there has nothing ever come out of antiquity that is any more historical than the sacred gospels.  Jesus Christ himself said, concerning the Ninevites, that, "They repented at the preaching of Jonah"  (Matthew 12:41).  To be sure the critics have tried every device known to them to get rid of that testimony in Matthew; but, as Bruce said, "The verse cannot be challenged on critical grounds."[40]