《资治通鉴·周纪·周纪五》
周子说： 赵国对于齐国、楚国来说，是一道屏障，就像牙齿外面的嘴唇，唇亡则齿寒。今天赵国灭亡了，明天灾祸就会降临齐国、楚国。
周子曰： 夫赵之于齐、楚，扞蔽也，犹齿之有脣也，脣亡则齿寒；今日亡赵，明日患及齐、楚矣。
Zhouzi said: The State of Zhao is a barrier for Qi and Chu, just like the lips outside the teeth. When the lips are gone, the teeth will feel the cold. If the State of Zhao is destroyed today, tomorrow disaster will befall Qi and Chu.