The Boy Who Cried Wolf
A shepherd boy, who tended his flock not far from a village, used to amuse himself at times in crying out "Wolf! Wolf!" Twice or thrice his trick succeeded; the whole village came running out to his assistance, when all the return they got was to be laughed at for their pains.
At last one day the wolf came indeed. The boy cried out in earnest. His neighbors, supposing him to be at his old sport, paid no heed to his cries, and the wolf devoured the sheep. So the boy learned, when it was too late, that liars are not believed even when they tell the truth.