斩草除根 — “To eradicate evil or trouble root and branch”

In the sixth year of Duke Yin's reign, the states of Wey and Chen jointly attacked the state of Zheng. Duke Zhuang of Zheng was defeated and sought peace with Duke Huan of Chen. Duke Huan refused. His younger brother advised him, 'Maintaining good relations with virtuous people and being friendly with neighboring states is the foundation of establishing a nation. You should make peace with him!' Duke Huan retorted angrily, 'Song and Wey are large states, and our state of Chen is no match for them; not fighting them is understandable. But Zheng is a small state, why shouldn't we attack it?' Thus, Duke Huan insisted on continuing the attack on Zheng.

Two years later, Zheng grew stronger and dispatched troops to attack Chen. Chen suffered a great defeat, and none of its neighboring states came to its aid.

Regarding this matter, the common people discussed, saying, 'Chen brought this upon itself, suffering the consequences of its own actions. This is the result of persistently doing evil without repentance. Ancient texts say that doing evil is easy, and evil is like a sudden wildfire on a prairie, impossible to extinguish, ultimately burning oneself. A high official of the Zhou Dynasty named Zhou Ren once articulated this principle: As the ruler of a state, one must be decisive. When dealing with evil people and evil deeds, one must be like a farmer weeding a field, digging them out by the roots, leaving no chance for them to grow again.'