《后汉书·列传·张曹郑列传》
你一定要奋勉努力，追求君子的修养，钻研不懈。要谨慎地注意自己的态度仪表，亲近那些有德行的人。
其勖求君子之道，研钻勿替，敬慎威仪，以近有德。
You must make every effort, and pursue the cultivation of a gentleman, and study without end. You must pay careful attention to your own conduct and demeanor, and come close to those of virtue.