Chen Sibai asked: “Did Duke Zhao understand the rites?” Confucius said: “Yes, he understood the rites.” Confucius withdrew. With a bow, Chen invited Wuma Qi to come forward and said to him: “I have heard it said that a true leader is never biased. But isn’t your master biased after all? The Duke took a wife from the state of Wu, but since she belonged to his own clan he changed her name to Wu Mengzi. If the Duke understood the rites, who doesn’t understand them?” Wuma Qi reported this to Confucius. Confucius said: “I am fortunate indeed: whenever I make a mistake, there is always someone on hand to let me know about it.”
Chen Sibai (陳司敗) is either the name of some unknown person or means the Minister of Crime for the state of Chen. No matter who he really is, he certainly thinks he is a clever chap by asking Confucius a loaded question as to whether Duke Zhao of the state of Lu understands the rites.
This is because he knows very well that Confucius has no choice but to defend his ruler, even though Confucius is well aware that the Duke violated an important social taboo by marrying a woman bearing the same clan name as his own (姬/Jī).
This naturally gives the cunning schemer the opportunity to voice his mock outrage at the Duke for trying to brush this unfortunate fact under the carpet by calling his wife Wu Mengzi (Mengzi of the state of Wu) rather than Ji Mengzi, not to mention throwing in a couple of digs at Confucius’s supposed lack of understanding of the rites as well.
Confucius responds in the best way possible with a heavy dose of sarcasm. He knows that he would have been criticized no matter how he had answered; all he can do is shrug and move on.
By the way, Wuma Qi was a disciple of Confucius.