桀犬吠尧 — “Jie's dog barks at Yao”

During the Western Han Dynasty, there was a scholar named Zou Yang. He first served King Liu Pi of Wu, but when the king plotted rebellion, Zou Yang disagreed and left. He then joined King Liu Wu of Liang. However, King Liang's trusted officials became jealous of Zou Yang and slandered him, leading to Zou Yang's imprisonment and facing execution.

From his prison cell, Zou Yang wrote a renowned letter to King Liang to defend himself, titled 'A Letter to King Liang from Prison.' In this letter, he cited numerous historical instances where loyal and capable individuals were unjustly accused or persecuted. He argued that if a lord could truly be open-minded and generous towards his subjects, 'then even Jie's dogs could be made to bark at Yao, and Zhi's followers could be made to assassinate You.'

Zou Yang's original intent was to illustrate that a benevolent and wise ruler could win over even the most unwavering supporters of a tyrant. However, the phrase '桀犬吠尧' (Jie's dog barks at Yao) evolved to metaphorically describe someone who, out of blind loyalty or servility, defends an evil or corrupt master against a righteous person or cause, akin to a tyrant's dog instinctively barking at anyone who approaches, regardless of their virtue.