脣亡齒寒

From the Commentary of Zuo:

晉侯復假道於虞以伐虢。宮之奇諫曰：「虢，虞之表也，虢亡，虞必從之。晉不可啟，寇不可翫。一之謂甚，其可再乎。諺所謂輔車相依，脣亡齒寒者，其虞虢之謂也。」 [Classical Chinese, trad.][▼ expand/hide]

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晋侯复假道于虞以伐虢。宫之奇谏曰：“虢，虞之表也，虢亡，虞必从之。晋不可启，寇不可玩。一之谓甚，其可再乎。谚所谓辅车相依，唇亡齿寒者，其虞虢之谓也。” [Classical Chinese, simp.]

From: Commentary of Zuo, circa 4^th century BCE

Jìn hóu fù jiǎdào yú Yú yǐ fá Guó. Gōng Zhīqí jiàn yuē: “Guó, Yú zhī biǎo yě, Guó wáng, Yú bì cóng zhī. Jìn bùkě qǐ, kòu bùkě wàn. Yī zhī wèi shèn, qí kě zài hū. Yàn suǒwèi fǔchēxiāngyī, chúnwángchǐhán zhě, qí Yú Guó zhī wèi yě.” [Pinyin]

The marquis of Jin once again wanted to attack Guo by way of Yu. Gong Zhiqi admonished the duke of Yu, saying, “Guo is exterior to Yu. If Guo should perish, Yu is sure to follow. The road should not be opened for Jin; the bandits are not to be ignored. Once was more than enough, how can you do it a second time? The two sayings, ‘The cheekbone and gum depend on one another’ and ‘When the lips perish, the teeth become cold’ both apply to the relationship between Guo and Yu.”

脣亡齒寒

1. to share a common lot; to share the same fate