During the Spring and Autumn period, the state of Qi had a minister named Yan Ying. Though short in stature and unremarkable in appearance, he was frugal in conduct and utterly devoted to his state.
When Yan Ying was sent as an envoy to the State of Chu, King Ling of Chu, proud of his kingdom's strength, looked down on Qi. He and his ministers devised a trap to humiliate Yan Ying.
When Yan Ying's carriage arrived at the eastern gate of Yingdu, the capital of Chu, the city gates were unexpectedly shut tight. A Chu guard approached and led him to a newly opened small side door, insisting he enter there. Yan Ying saw through their deliberate insult and replied with a cold smile, "Only those sent as envoys to a dog kingdom would enter through a dog door. I am here as an envoy to the state of Chu—there is no reason for me to go through this!"
The guard, left speechless, could only report back to the King of Chu
The next day, Yan Ying appeared before the King of Chu, with civil and military officials already lining both sides of the hall. Some ministers, looking down on Yanzi, hurled provocative questions to trap him, but Yanzi, quick-witted and sharp, refuted each one in turn.
Soon, King Ling of Chu swaggered into the hall. Yanzi stepped forward to pay respects, and the king deliberately shrugged, feigning confusion, and asked, "Is there truly no one left in your state of Qi?"
Yanzi replied, "In our state of Qi, the capital Linzi alone has thirty thousand households. If everyone spread their sleeves, they could form a canopy of shade; if everyone wiped their sweat together, it would become a shower. On the main roads, people stand shoulder to shoulder and heel to heel—it's bustling with activity. How can you say there are no people?"
"Since that's the case, how could the King of Qi send someone like you as an envoy to our state of Chu?" the King of Chu said disdainfully.
Yanzi replied calmly, "In our state of Qi, there is a rule for appointing envoys: virtuous and talented people are sent to states with wise rulers, while useless people are sent to states with foolish rulers. In our court, I, Yan Ying, am the most useless, so I had to be sent to your esteemed state."
The King of Chu had intended to humiliate Yanzi, but instead found himself mocked by the diplomat. Impressed, he recognized Yanzi as a rare talent in foreign affairs and received him with grand ceremony.
Later, people used the idiom "Shoulder to Shoulder, Heel to Heel" to describe a large, crowded crowd.
Source: *Yanzi's Spring and Autumn Annals*, Chapter "Miscellaneous Matters"
Meaning of the Idiom: Later, the Chinese idiom "比肩继踵" came to describe a large, crowded crowd.