Jonah 3:1

Arise, go unto Nineveh, that great city, and preach unto it the preaching that I bid thee.

So Jonah arose, and went unto Nineveh, according to the word of the LORD. Now Nineveh was an exceeding great city of three days' journey.

And Jonah began to enter into the city a day's journey, and he cried, and said, Yet forty days, and Nineveh shall be overthrown.

So the people of Nineveh believed God, and proclaimed a fast, and put on sackcloth, from the greatest of them even to the least of them.