During the late Eastern Han Dynasty, Sun Ce's power base in Jiangdong was formidable
Wu Commandery Governor Xu Gong secretly submitted a memorial to Emperor Xian of Han, saying, "Sun Ce is a very fierce man; it would be best to recall him to the capital. If he is allowed to remain outside, he will surely become a menace."
Unfortunately, the messenger carrying the letter was captured by Sun Ce's soldiers and reported to Sun Ce. Upon reading Xu Gong's memorial, Sun Ce flew into a rage, devised a plan to lure Xu Gong in, and immediately had him strangled to death.
After Xu Gong was killed, his three retainers fled and, burning with vengeance, searched tirelessly for an opportunity to avenge their master.
Learning that Sun Ce loved hunting, his enemies tracked him to the western hills of Dantu, where he was chasing a deer alone on his fine horse. Suddenly, three former retainers of Xu Gong leaped from the roadside and ambushed him.
Before Sun Ce could react, an arrow struck him in the cheek, knocking his weapon from his hand
The three retainers gave chase without relenting. In that split-second moment of crisis, Sun Ce's attendants arrived just in time and killed all three retainers.
Back at his residence, Sun Ce's arrow wound flared up severely. Knowing he wouldn't live much longer, he summoned his younger brother Sun Quan and Chief Clerk Zhang Zhao, saying, "The chaos under heaven has just begun. With the people of Wu and Yue and the natural defenses of the Yangtze River, we have enough to contend for the realm. I hope you will properly assist my brother."
After speaking, he handed the seal and ribbon to Sun Quan and said, "If you mobilize the people of Jiangdong to wage war and contend for the realm, you are not as capable as I am. But in employing virtuous talents and making them devote themselves wholeheartedly to defending Jiangdong, I am not as capable as you."
Sun Quan, overcome with grief, wept uncontrollably as he knelt to receive the imperial seal and sash.
After Sun Ce's death, Sun Quan mourned endlessly. Zhang Zhao thus admonished him, pointing out that wolves now blocked the path and many sought rebellion; if he only grieved for his brother and neglected state affairs, it would be like "opening the door to invite a robber"—inviting disaster upon himself.
Upon hearing this, Sun Quan felt the weight of his responsibility, held back his tears, and immediately changed his clothes to inspect the troops.
With the Kingdom of Wu quickly gaining a new ruler, Zhang Zhao and others helped Sun Quan govern with diligence and vigor, and before long, the three kingdoms of Shu, Wei, and Wu stood in a tripartite balance of power.
Later, people used the idiom "Opening the Door to Welcome a Thief" to describe inviting trouble by letting in bad elements.
Source: *Records of the Three Kingdoms*, Book of Wu, "Biography of Sun Quan"
Meaning of the Idiom: Later, the Chinese idiom "开门揖盗" came to describe inviting trouble by letting in bad elements.