A wolf in sheep's clothing

A cunning wolf could not penetrate the sheep pen no matter how hard it tried. A farmer was always on guard keeping a careful watch. One day, it disguised itself as a sheep. It wrapped itself with sheepskin. It crept into the flock and waited for the right moment to catch one for its meal. The alert farmer saw the thief among his flock. He hung him up, sheepskin and all, as a spectacle and an example.