English Original
During the Spring and Autumn Period (770–476 BC), Duke Xian of the State of Jin sought to expand his power and sphere of influence. He planned to attack the State of Guo, claiming it had encroached on Jin's borders. However, the State of Yu lay between Jin and Guo, forcing the Jin army to pass through Yu.
"How can my army cross Yu without a hitch?" Duke Xian asked his ministers. Minister Xun Xi replied, "The ruler of Yu is short-sighted and covets small gains. If we offer him precious stones and fine horses, he will likely grant us passage."
Seeing Duke Xian's reluctance, Xun Xi continued, "Yu and Guo are as closely related as lips and teeth. If Guo is destroyed, Yu cannot survive alone. Your treasures are merely being stored with the ruler of Yu for now."
Duke Xian agreed. The ruler of Yu, delighted with the gifts, readily promised passage. Upon hearing this, Minister Gong Zhiqi of Yu urgently admonished his ruler: "This will not do. Yu and Guo are interdependent like lips and teeth. If Guo falls, Yu will be in peril. As the saying goes, 'If the lips are gone, the teeth will be cold.' We must not allow the Jin army through."
The ruler of Yu said, "Jin is a major state offering us gifts in friendship. How can we refuse them?" Gong Zhiqi sighed repeatedly and, foreseeing Yu's doom, left with his family.
As predicted, the Jin army passed through Yu, destroyed Guo, and on their return captured the welcoming ruler of Yu, destroying Yu as well.
This story from Zuo Qiuming's commentary Zuo Zhuan ("The Fifth Year of Duke Xi") gives rise to the idiom "If the lips are gone, the teeth will be cold," meaning that interdependent parties share a common fate; if one falls, the other is endangered.
中文翻译
春秋时期（公元前770-476年），晋献公企图扩张自己的实力和势力范围。他计划攻打虢国，借口是虢国时常侵犯晋国边境。然而，虞国位于晋国和虢国之间，晋军必须经过虞国才能到达虢国。
"我军如何才能顺利通过虞国呢？"晋献公问他的大臣。大夫荀息说："虞国国君目光短浅，贪图小利。如果我们献上珍贵的宝玉和骏马，他很可能会允许我军通过。"
看到晋献公有些舍不得，荀息接着说："虞国和虢国是唇齿相依的邻邦。如果虢国灭亡了，虞国也不能独自生存。您的宝物不过是暂时存放在虞君那里罢了。"
晋献公同意了。虞国国君见到珍贵的礼物喜出望外，爽快地答应了借道。听到这个消息，虞国大夫宫之奇急忙劝谏国君："这不行啊。虞国和虢国是唇齿相依、互为依存的邻邦。如果虢国灭亡了，我们虞国也就危险了。俗话说：'唇亡齿寒'。我们绝不能允许晋军通过。"
虞国国君说："晋国是大国，特意送来礼物想与我们友好。在这种情况下，我们怎么能拒绝他们借道呢？"宫之奇连连叹息，预见到虞国将亡，便带着全家离开了虞国。
果然，晋军借道虞国，消灭了虢国，回师途中又俘获了亲自出来迎接的虞国国君，顺势也将虞国灭亡了。
这个故事出自左丘明对《春秋》的注释《左传》（《僖公五年》），并产生了成语"唇亡齿寒"，用来比喻双方关系密切，利害与共，一方受损，另一方也必然受到危害。