《北史·列传·卷三十》
孝文帝派人对他说 ：我虽然几天不吃饭，还没有什么感觉，这是我诚心未至的原因啊。
帝遣答曰： 虽不食数朝，犹然无感，朕诚心未至之所致也。
Emperor Xiaowen sent someone to tell him: Although I haven't eaten for a few days, I don't feel anything yet. This is because my sincerity is not enough.