《资治通鉴·齐纪·齐纪六》
崔庆远说：  见可而进，知难而退 ，这样就是圣人之师。 孝文帝又问道： 您希望与我和睦友好呢？
如卿之言，便可释然。 庆远曰：  见可而进，知难而退 ，圣人之师也。 
Cui Qingyuan said: If we can, we step forward; if we know it is difficult, we retreat, which is the teacher of Saint person. Xiao Wendi asked again: Do you hope to get along well with me?