The mouse and the frog

A mouse asked a frog,"Will you carry me on your back,across the water?I promise i will not bite you." The frog agreed.When they reached the middle of the stream suddenly the mouse bit the frog.The frog cried out in pain and started drowning.He asked the mouse "You promised not to bite me!" The mouse replied "You stamped my tail once this was my revenge." The frog said,"Silly mouse!I am dying but you will also sink with me and drown to death.

Moral-Revenge harms it victim as well as the one who takes it.