《资治通鉴·汉纪·汉纪三十五》
皇太子曾向他请教打仗的事，刘秀说： 从前卫灵公请教战争的事，孔子不肯答复。
皇太子尝问攻战之事，帝曰： 昔卫灵公问陈，孔子不对。
The crown prince once asked him about fighting, and Liu Xiu said: "In the past, when Duke Ling of Wei asked Confucius about war, Confucius refused to answer."