《淮南子·人间训》
于是张孟谈暗中出城会见魏、韩两君王，劝说道： 人们常说：唇亡齿寒。
乃见韩、魏之君，说之曰： 臣闻之，唇亡而齿寒。
So Zhang Mengtan secretly went out of the city to meet the monarchs of Wei and Han, and advised: People often say: The lips are dead and the teeth are cold.