This sentence was said by Li Shimin, Emperor Taizong of the Tang Dynasty. The original sentence is (Taizong said to Liang Gong: Use copper as a mirror, you can straighten your clothes; use ancient times as a mirror, you can know the rise and fall; use people as a mirror, you can know gains and losses. I have tasted these three mirrors to guard against my own mistakes. Now Wei Zheng If you die, you will lose a mirror.) Using copper as a mirror, you can straighten your clothes; using history as a mirror, you can know the ups and downs; using people as a mirror, you can understand gains and losses. Using copper as a mirror, you can organize a person's clothes; using history as a mirror, you can know the rise and fall of history; using others as your own mirror, you can know your gains and losses every day. Quotations from "Song Dynasty Ouyang Xiu and Song Qi Xin Tang Shu Volume 110 Biography 22 Wei Zheng": "Use copper as a mirror to correct the bandits; use the ancients as a mirror to know the rise and fall; use people as a mirror , I can understand the gains and losses. I try to protect myself from my mistakes. Now that the Wei Dynasty has passed away, one of the lessons will be lost. "Li Shimin, Emperor Taizong of the Tang Dynasty, liked to listen to all kinds of suggestions, and he knew well that "listening to both sides will make you aware, and partial belief will bring you darkness." principle. His direct remonstrance minister Wei Zheng once went to dozens of meetings to directly state his faults, and advised Taizong to reflect on himself, be prepared for danger in times of peace, listen to good advice, and choose the good and follow it. After the death of Zheng in the later Wei Dynasty, Taizong came to express his condolences in person. He cried bitterly and sighed: "Using copper as a mirror can make you look dignified and neat when wearing it; using history as a mirror, you can know the rise and fall of the past dynasties; 'using people as mirrors' can be seen." People's actions are used to determine their own gains and losses. I always keep these three mirrors to prevent myself from making mistakes. Now that Wei Zheng is dead, I have lost one mirror.

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