During the Warring States period, Fan Sui of the state of Wei accompanied the imperial advisor Xu Jia on a diplomatic mission to the state of Qi.
King Xiang of Qi heard that Fan Ju was a brilliant debater, so he sent an envoy to bestow upon Fan Ju ten jin of gold along with beef and wine as imperial gifts. Fan Ju declined the offerings, refusing to accept them.
When Xu Jia learned of this, he was furious, convinced that Fan Ju had betrayed Wei's state secrets to Qi in exchange for those imperial gifts. Upon returning to Wei, Xu Jia reported to Prime Minister Wei Qi, 'Fan Ju has sold us out for Qi's rewards!'
When Wei Qi heard this, he flew into a rage and ordered his attendants to beat Fan Ju with whips, breaking his ribs and knocking out his teeth. Fan Ju pretended to be dead, so the attendants wrapped him in a straw mat and threw him into the latrine. At that time, Wei Qi was hosting a banquet, and the drunken guests, in a deliberate act of humiliation, all urinated on him.
After being rescued, Fan Ju fled to the state of Qin, changed his name to Zhang Lu, and was appointed prime minister by the King of Qin, becoming a powerful figure holding the administrative reins of the state.
At that time, the State of Qin was about to attack the State of Wei, so Wei sent Xu Jia to Qin to plead for mercy. When Xu Jia arrived in Qin, Fan Ju changed into tattered clothes and disguised himself as a poor man to meet him. Xu Jia, seeing him, said sympathetically, "How could Fan Shu have fallen into such poverty!" and gave him a silk robe.
When Xu Jia arrived at the prime minister's residence to pay respects to Prime Minister Zhang Lu, he was shocked to discover that Zhang Lu was actually Fan Ju, and immediately fell to his knees, begging for forgiveness.
Fan Ju said, "The only reason you get to live today is because of the lingering affection you showed by giving me that robe—proof that some old friendship still remains. That's why I'm sparing you." He continued, "Go back and tell the King of Wei for me: send Wei Qi's head immediately."
When Xu Jia returned to the state of Wei, he reported the matter to Wei Qi, who was so terrified that he fled to the state of Zhao and hid in the residence of Lord Pingyuan. Yet, in the end, he could not escape death.
Later, the idiom "the feeling of a silk robe" came to be used as a metaphor for not forgetting old friendships.
Source: *Records of the Grand Historian*, "Biography of Fan Ju"
Meaning of the Idiom: Later, the Chinese idiom "绨袍之情" came to describe not forgetting old friendships.