In 506 BCE, the Chu official Wu She was executed, and his younger son Wu Zixu fled to the state of Wu. There, he led a Wu army to breach Chu's capital, forcing King Zhao of Chu to flee in panic to the state of Sui. Wu Zixu then scoured the land for King Zhao, determined to avenge his father's death.
Actually, Wu She had been killed by King Ping, the father of King Zhao. By the time King Ping was already dead, Wu Zixu dug up his grave, dragged out the corpse, and beat it to a pulp with an iron whip before seeking vengeance against King Zhao himself.
Wu Zixu's close friend Shen Baoxu sent him a letter saying, "Things will turn when they reach their extreme; you should stop while you can!" Wu Zixu did not heed Shen Baoxu's advice and replied, "To avenge my father, I cannot spare the state of Chu." Upon receiving the letter, Baoxu sighed and said, "Wu Zixu wants to destroy Chu—how can I stand by and do nothing to save it!"
Shen Baoxu knew that King Ping of Chu's wife was the daughter of Duke Ai of Qin, so he decided to seek aid from Qin. Racing day and night, he rushed to the Qin court, covering a thousand li in a single day.
Shen Baoxu pleaded with the Duke of Qin for military aid, but the duke refused, citing Qin's remote location and scarce troops. Shen then appealed to their familial bond as uncle and nephew, yet the duke still declined, telling Shen to rest at the guesthouse while he consulted his ministers.
But the King of Qin, lost in days of wine and women, completely forgot about the matter. Shen Baoxu, refusing to remove his court robes or hat, stood in the Qin palace courtyard, weeping day and night, eating and drinking nothing for seven full days. Deeply moved by Shen Baoxu's anguished cries, Duke Ai of Qin personally went to comfort him and sang the song *No Clothes*: "How can you say you have no clothes? I will share my robe with you. The king is raising an army, let us sharpen our weapons and face the common foe together..."
Upon hearing the lyrics speak of sharing clothes and avenging wrongs together, along with repairing weapons and preparing for battle, Shen Baoxu realized that Duke Ai had agreed to send troops. He immediately kowtowed in gratitude and resumed eating and drinking.
Shen Baoxu finally secured the rescue troops and saved the state of Chu.
Later, people used the idiom "Common Hatred Against the Enemy" to refer to a shared feeling of resentment and anger toward an adversary.
Source: *Book of Songs*, "Airs of Qin", "No Clothes"
Meaning of the Idiom: Later, the Chinese idiom "同仇敌忾" came to describe a shared feeling of resentment and anger toward an adversary.