“When God saw

What they did,

How they turned

From their evil ways,

God changed his mind

About the calamity

That he had said

He would bring upon them.

Thus,

He did not do it.”

This is one of the few cases where God changing his mind.  God did not bring destruction to Nineveh.  God saw how the people and the leaders of Nineveh had turned from their evil ways.  Thus, he decided not to bring destruction to this non-Israelite town, because of their repentance.  God showed mercy to them.