During the Han Dynasty, the famed general Li Ling led his troops to attack the Xiongnu but was unfortunately defeated and surrendered.
When Emperor Wu of Han heard that Li Ling had surrendered to the Xiongnu, he flew into a rage and denounced Li Ling as a traitor, with many courtiers joining in the condemnation. Only Sima Qian defended him, arguing, "Li Ling is not truly surrendering; he is waiting for a chance to redeem himself through merit."
Emperor Wu of Han was furious when he learned that Sima Qian had dared to defend Li Ling, and immediately ordered Sima Qian thrown into a dark prison and subjected to the cruel punishment of castration.
Sima Qian considered ending his own life, but then thought that as a lowly person, even if he died, in the eyes of the emperor and ministers, it would be like "losing one hair from nine oxen"—utterly insignificant.
Thus, he abandoned the thought of suicide and resolved to live on with resilience. Sustained by this unyielding spirit, he endured immense hardships in prison and finally completed the great masterpiece *Records of the Grand Historian*, a work that would echo through the ages.
Later, people simplified Sima Qian's phrase "one hair lost from nine oxen" into the idiom "a single hair from nine oxen," used to describe an extremely small and insignificant fraction of a vast quantity.
Source: *Report to Ren Shaoqing*
Meaning of the Idiom: Later, the Chinese idiom "九牛一毛" came to describe an extremely small and insignificant fraction of a vast quantity.