GuruBear- The Sharpest Spear and the Strongest Shield
The story described how a weapon-selling street vendor humiliated himself in the market. He first bragged that he had the sharpest spear and then continued to boast about his strongest shield. But when one of the spectators asked him what would happen if he stabbed his spear into his shield, he became speechless.
The moral of the story is to warn a person to be careful not to contradict his own words.