During the Spring and Autumn period, the great educator Confucius had many students, including one named Ziyu, who was very ugly, and another named Zaiyu, who was very handsome. Confucius treated them very differently.
Ziyu was so ugly that Confucius formed a poor impression of him at first sight. Confucius thought to himself, "This man looks like a monster; he must have no talent."
As a result, Confucius treated Ziyu coldly, and Ziyu eventually had to drop out and pursue his studies alone.
Confucius was particularly fond of his disciple Zai Yu, charmed by his handsome appearance, elegant demeanor, and silver-tongued eloquence, believing this student was destined for great success.
However, things did not go as Confucius had expected. Ziyu, a man who loved learning and independent thought, studied even harder after leaving Confucius and became a renowned scholar. Many young people came to study under him, and his fame spread among the feudal lords.
In stark contrast, Zai Yu was exceptionally lazy. Despite Confucius teaching him with great care, his academic performance was abysmal. Confucius repeatedly advised him, but Zai Yu refused to listen. Sometimes, even after the sun was fully up, he would still be lounging in bed. Frustrated, Confucius compared him to useless rotten wood.
Later, Zai Yu, relying on his eloquence, secured an official position in the state of Qi, but before long, he was executed by the King of Qi for joining a rebellion.
When Confucius heard of Zai Yu's death, he said with deep emotion, "From Ziyu I learned that a person cannot be judged by appearance; and from Zai Yu I learned that a person cannot be judged by what he says."
Later, the idiom "judging by appearance" came to describe evaluating someone's character and abilities solely based on their looks.
Source: *Records of the Grand Historian*, "Biographies of the Disciples of Confucius"
Meaning of the Idiom: Later, the Chinese idiom "以貌取人" came to describe evaluating someone's character and abilities solely based on their looks.