Zhao Guanghan, a Han Dynasty official known for his integrity and sharp administrative skills, once uncovered a case of stolen imperial gifts from the emperor. When a palace servant was suspected, Zhao interrogated him directly: "These items were bestowed by the throne—how did they end up in your hands?" The servant stammered, "I... I found them discarded." Zhao pressed, "Discarded? The emperor's gifts are never thrown away. Speak the truth, or face the law." The servant confessed, revealing a network of corruption. Zhao's swift justice earned him fame as a master of uncovering deceit. Source: *Book of Han*, "Biography of Zhao Guanghan"
Zhao Guanghan was a man of bold vision, skilled in using the "hook-and-compare" method to uncover the truth of any matter. This method worked like this: to determine the price of a horse, he would first ask about the price of a dog, then a sheep, then an ox, and only finally the horse—by comparing similar items, he could gauge whether the horse's price was accurate. Zhao Guanghan alone mastered this technique and applied it flawlessly; none who tried to imitate him could match his skill. He knew every detail about the county's thieves, local bullies, and even which of his subordinates secretly took bribes.
One day in Chang'an, a group of young men gathered in a secluded spot to plot a robbery. Before they could finish their scheme, Zhao Guanghan sent officers to arrest and interrogate them. They immediately confessed to the crime.
When a wealthy man named Su Hui was taken hostage by two bandits demanding a huge ransom, Zhao Guanghan, the governor, arrived swiftly and stood outside their door. He ordered the county magistrate Gong She to knock and warn the criminals, 'Do not harm the hostage—he is an imperial guard. Release him and surrender, and you will be treated well. If you happen to receive a general amnesty from the emperor, you might even escape execution.' The two bandits, stunned that Zhao Guanghan had tracked them so quickly and terrified by his legendary reputation, immediately opened the door, knelt, and confessed their crime. Zhao Guanghan thanked them, saying, 'Fortunately, Su Hui is alive, and I will treat you well.' He sent them to prison, where the jailers provided fine food and drink daily. When winter came and they were sentenced to death, Zhao Guanghan even prepared coffins and burial items for them, explaining the situation honestly. Both men declared, 'We die without regret!'
Zhao Guanghan once invited a local constable from Hudu to meet him. As the constable traveled west to the border, the constable at the border gate joked, "When you reach the capital, say hello to Zhao Guanghan for me!" When the Hudu constable arrived at the capital, after their conversation, Zhao Guanghan remarked, "The border constable asked you to pass along a greeting—why didn't you deliver it for me?" The Hudu constable was deeply impressed, kowtowed, and admitted it was true. Zhao Guanghan then said, "Go back and thank the border constable for me. Tell him to work hard—I won't forget his kindness."
Zhao Guanghan was a master of catching criminals and uncovering hidden truths, with an almost supernatural ability to predict events—his achievements were too numerous to count. Under his governance, the capital region enjoyed peace and order, earning him endless praise from the people, who declared that no one since the Han Dynasty's founding had governed the capital as well as he did. His reputation even spread to the Xiongnu tribes.
Later, the idiom "Ask the Ox, Know the Horse" came to mean inferring from indirect clues to understand the truth.
Source: *Book of Han*, "Biography of Zhao Guanghan"
Meaning of the Idiom: Later, the Chinese idiom "问牛知马" came to describe inferring from indirect clues to understand the truth.