《左传·僖公·僖公三十年》
佚之狐对郑文公说： 国家危急了。假若派遣烛之武去进见秦君，军队必然退走。 
佚之狐言于郑伯曰： 国危矣，若使烛之武见秦君，师必退。 
Yizhihu spoke to Duke Wen of Zheng, saying: The state is in danger. If you send Zhuzhiwu to meet the King of Qin, the army will certainly retreat.