The people of Nineveh believed God; and they proclaimed a fast, and put on sackcloth, from the greatest of them even to the least of them.
There is also another very important possibility, and that regards the matter of Jonah's appearance following his deliverance.  Many writers have wondered if he carried in his body any evidence of the terrible ordeal through which he had passed.  Was his skin forever altered in color by the digestive juices in the fish?  Were there scars that he would carry to the grave?  We have no answers to such questions; but our Lord Jesus Christ exhibited the pierced hands and feet, and invited Thomas to thrust his hand into our Saviour's side after the resurrection!  Again, the likeness between the antitype and type suggests that one of the ways in which Jonah was a sign to the Ninevites might very well have been that of the evidence exhibited in his body of what had occurred.  Certainly, it was true in the case of Jesus our Lord.