During the final years of the Qin Dynasty, a man named Ji Bu from the Chu region (modern-day Jianghuai basin) earned a reputation among his peers for his skill with the sword and his unwavering commitment to his word. His integrity was so renowned that even chivalrous knights from the north had heard of him. A popular saying spread among the people: "A hundred catties of gold is not worth one promise from Ji Bu."
During the great peasant uprising at the end of the Qin Dynasty, Ji Bu joined Xiang Yu's army. His bravery and skill in battle earned him Xiang Yu's high regard. After the Qin Dynasty fell and the Chu-Han conflict erupted, Ji Bu led Chu forces to repeatedly defeat the Han army, earning Liu Bang's deep hatred.
In 206 BC, Liu Bang defeated Xiang Yu and unified China. After becoming emperor, he offered a reward of a thousand taels of gold for Ji Bu's capture and declared that anyone daring to harbor Ji Bu would have their entire clan executed.
When Ji Bu heard the news, he went into hiding at the home of the famous Luodi knight-errant Zhu Jia, who had long admired Ji Bu and was determined to save him. Zhu Jia personally traveled to Luoyang to visit the Marquis of Ruyin, Teng Gong, and said, "Ji Bu once fought for Xiang Yu, but that was simply each man serving his own master and fulfilling his duty as a subject. Now that the emperor has just unified the realm, pursuing Ji Bu over a personal grudge seems unwise. If Ji Bu were to flee to another state, he would become a great threat to Han. Please advise the emperor!"
Upon hearing Zhu Jia's defense, Lord Teng suspected that Ji Bu was hiding in Zhu Jia's home, but found his reasoning sound. Seizing an opportunity, Lord Teng advised Liu Bang to pardon Ji Bu. The emperor agreed, and Ji Bu was soon summoned to court, where he was appointed a palace attendant.
By the time of Emperor Wen of Han, Ji Bu had become a renowned minister at court. Later, the emperor appointed him as the Governor of Hedong Commandery (in present-day southwestern Shanxi Province). Though his rank had risen, his straightforward nature remained unchanged. At that time, there was a man named Cao Qiusheng, who was eloquent and fond of currying favor with the powerful. Ji Bu deeply despised him.
Once, Ji Bu heard that Dou Changjun was closely associating with Cao Qiusheng, so he wrote to advise Dou Changjun: "Cao Qiusheng is not a man of integrity; I hope you will not associate with him."
When Cao Qiusheng heard of this, he ignored Dou Changjun's warnings and insisted on meeting Ji Bu. Dou Changjun reluctantly wrote a letter of introduction and sent it ahead to Ji Bu.
Ji Bu, knowing that Cao Qiusheng was coming, waited angrily in the living room. As soon as Cao Qiusheng entered, he bowed and smiled, saying, "There's a saying in Chu: 'A hundred jin of gold is not worth one promise from Ji Bu.' You have such a fine reputation, all thanks to the people of Chu spreading it. I am also from Chu—why do you despise me?"
Ji Bu, upon hearing Cao Qiusheng's humble words, saw his anger vanish completely. He kept Cao as a guest for several months and, when Cao departed, showered him with gifts. In return, Cao Qiusheng tirelessly spread Ji Bu's reputation far and wide, making his name ever more renowned.
Later, people used the idiom "A Promise Worth a Thousand Gold" to describe someone who keeps their word and is extremely trustworthy.
Source: *Records of the Grand Historian*, "Biographies of Ji Bu and Luan Bu"
Meaning of the Idiom: Later, the Chinese idiom "一诺千金" came to describe how someone who keeps their word and is extremely trustworthy.