Aesop's Fables
#299 The Viper and the File
A Viper, entering the workshop of a smith, sought from the tools the means of satisfying his hunger. He most particularly addressed himself to a File, and asked of him the favor of a meal.
The File replied, "You must indeed be a simple-minded fellow if you expect to get anything from me, who am accustomed to take from everyone, and never to give anything in return."