During the Spring and Autumn period, the southern state of Chu was a major power, while Zheng was a small state bordering it to the north.
Once, Prince Wei of Chu (later King Ling of Chu) planned to visit the state of Zheng, and Zheng, eager to strengthen ties, had the nobleman Gongsun Duan betroth his daughter to the prince. But Chu saw an opportunity to strike, secretly sending an army with Prince Wei under the guise of a wedding escort, hoping to catch Zheng off guard.
The Chu army was about to enter the city. Zichan, the chief minister of Zheng, saw through Chu's intentions and sent Ziyu to politely decline outside the city. Ziyu said to the wedding party:
"Since our capital is small and cannot accommodate so many attendants, please allow us to sweep the ground outside the city and hold the ceremony there!"
The prime minister of Chu sent Grand Steward Bozhou Li to reply:
The envoy of Chu replied, "Our lord has graciously bestowed favor upon Prince Wei, who solemnly reported to his ancestors before departing for Zheng. If the wedding ceremony is now held in the wilderness, it would be like casting your state's kindness into the weeds, while also causing Prince Wei to commit the crime of deceiving his ancestors. In that case, he could no longer serve as a minister of our state. We ask you to consider this carefully."
At this point, Ziyu adopted a stern tone and said:
The envoy of the small state replied, "A small state is not a crime; relying on a great power without preparing for danger is its true fault. A small state seeks security through a great power, but if that great power harbors ill intentions and covets its territory, it will only stir resentment among all the other states! Our capital is merely a guesthouse for your lord, so how could our ruler begrudge his own ancestral temple?"
Realizing that Zheng had seen through their plan and prepared defenses, the Chu scouts concluded there was little to gain, so they abandoned the surprise attack, requesting instead to enter the city with their bows and quivers slung upside down—a sign of peaceful intent. The Zheng officials agreed to this request.
Later, the idiom "harboring evil intentions" came to describe someone secretly harboring malicious thoughts.
Source: *Zuo Zhuan*, "First Year of Duke Zhao"
Meaning of the Idiom: Later, the Chinese idiom "包藏祸心" came to describe how someone secretly harbors malicious thoughts.