《后汉书·列传·杜栾刘李刘谢列传》
没有取得皇上的信任，对皇上进行谏诤，皇上就认为谏诤是诽谤自己。所以说话应该懂得说话的难处啊！
夫未信而谏，则以为谤己，故说者识其难焉。
Without winning the emperor’s trust, if one dares to criticize the emperor, the emperor will think that the criticism is slandering him. Consequently, one should know the difficulty in speaking!