用銅做鏡子，可以整理好一個人的穿戴；用別人作自己的鏡子，可以知道自己每一天的得失；用歷史作為鏡子，可以知道歷史上的興盛衰亡。

With bronze as a mirror one can dress neatly; with the example of another person one can see the advantages and disadvantages of himself; from the mirror of history one can know the reason for the rise and fall of states.

Source: Tatoeba