During the Ming Dynasty, the emperor issued an edict banning the slaughter of plow oxen, with no exceptions—not even for those who followed the Islamic faith.
One day, the country squire Zhang Jingzhai and the successful candidate Fan Jin visited Magistrate Tang Feng of Gaoyao County. Magistrate Tang hosted a banquet for them. During the meal, an elderly man brought Tang a gift of fifty jin of beef, pooled together by several Muslim followers. Tang, a corrupt official who also practiced Islam, hesitated due to a ban on slaughtering cattle. He turned to Zhang Jingzhai and asked, "You've served as an official—this matter of banning cattle slaughter needs your advice. Some Muslims have sent fifty jin of beef to request leniency. Should I accept it or not?"
Zhang Jingzhai shook his head and said, "This absolutely won't do. As officials, our hearts should belong only to the emperor—how can we care about those who share our faith? Remember Minister Liu (Liu Ji, also known as Liu Bowen) during the Hongwu era? The emperor visited his home incognito and happened to see a jar of pickled vegetables sent by King Zhang of Jiangnan (Zhang Shicheng). When opened, it turned out to be a jar of gold nuggets. The emperor was furious and demoted Minister Liu to magistrate of Qingtian County the next day, later poisoning him to death."
Magistrate Tang, thoroughly convinced by Zhang Jingzhai's eloquent reasoning, urgently asked for his advice on how to handle the matter. Zhang Jingzhai replied, "Sir, you can make a big issue out of this. Arrest that old man, give him several dozen lashes, put a heavy cangue on him, pile the beef he brought on top of the cangue, and post a notice beside it stating that they acted recklessly and knowingly broke the law. If your superiors see that you handle matters with such meticulous care, your promotion and fortune will be just around the corner."
Magistrate Tang nodded repeatedly, "Perfectly reasonable." And so he proceeded accordingly. Later, the idiom "meticulous in every detail" came to describe being thorough and careful in one's work, without the slightest negligence.
Source: *The Scholars*
Meaning of the Idiom: Later, the Chinese idiom "一丝不苟" came to describe how being thorough and careful in one's work, without the slightest negligence.