Confucius once said, "Hearing groundless talk on the road and irresponsibly spreading it along the way is morally unacceptable."
During the Warring States period, the scholar Aizi returned to the state of Qi from Chu. Just as he entered the capital, he ran into the boastful Mao Kong, who whispered with great mystery, "A family's duck just laid a hundred eggs at once!"
Mao Kong insisted to Ai Zi, "A duck laid a hundred eggs!" Ai Zi replied, "That's impossible." Mao Kong quickly changed his story, "Then maybe it was two ducks." Ai Zi shook his head, "Still impossible." Mao Kong kept adjusting, "Perhaps three ducks, or four, eight, ten!" But he refused to reduce the total number of eggs, so Ai Zi remained skeptical. A moment later, Mao Kong added, "Last month, a piece of meat fell from the sky—thirty zhang long and ten zhang wide!" Ai Zi again doubted him, and Mao Kong hastily revised, "Then twenty zhang long." When Ai Zi still wouldn't believe, Mao Kong said, "Fine, let's say ten zhang!"
Ai Zi could no longer contain himself and refused to listen to Mao Kong's wild boasting any longer. He retorted, "How could there be a piece of meat ten zhang long and ten zhang wide in this world? And would it fall from the sky? Did you see it with your own eyes? Which family did the duck you mentioned earlier belong to? And where exactly did this big piece of meat fall?"
Mao Kong was stumped and could only stammer, 'I heard it all from people on the road.' Ai Zi laughed and turned to his students, saying, 'Do not be like him, spreading "roadside gossip"!' This story from the Ming Dynasty joke collection *Aizi's Outer Sayings* by Tu Benjun illustrates Confucius's teaching: 'To repeat what you hear on the road is to abandon virtue.' The idiom "dao ting tu shuo" originally meant passing along rumors heard on the street, later referring to any unfounded hearsay.
Source: *The Analects*, Chapter "Yang Huo"
Meaning of the Idiom: Later, the Chinese idiom "道听途说" came to describe any unfounded hearsay.