《北史·列传·卷二十八》
显宗回答： 陛下认为物不可类聚，不应该老是让贵族的后代继承前代的职务，卑贱的就永远只能承袭卑贱的职务。 
显宗曰： 陛下以物不可类，不应以贵承贵，以贱袭贱。 
Xianzong replied: Your Majesty believes that things should not be classified together, and the descendants of nobles should not always inherit the positions of their ancestors, and the lowly should only inherit the lowly positions forever.