刮目相看 — “To regard someone with new eyes”

During the Three Kingdoms period, there was a general named Lü Meng in the state of Wu. He came from a poor family and, lacking the opportunity for formal education, followed his brother-in-law to join the army. He was very brave in battle and eventually earned the appreciation of Sun Quan, the emperor of Wu.

Initially, Lü Meng was illiterate and believed that bravery alone was sufficient for success. One day, Sun Quan earnestly advised Lü Meng, 'You are now a pillar of the state; you must study hard!' Lü Meng jokingly replied, 'I'm busy fighting all day; where do I find time to study, haha?' Sun Quan became serious, 'I, the king, am probably even busier than you! I've read so many books and still feel it's not enough. I still make time to read various historical and military texts, which is very beneficial. Look at Cao Cao, even at his old age, he remains eager to learn. Please don't take my words as a joke.' From that moment, Lü Meng resolved to study whenever he had spare time, and his knowledge and insights grew rapidly.

One day, the renowned scholar Lu Su discussed state affairs with Lü Meng. Lu Su often found himself at a loss for words when questioned by Lü Meng. Lu Su was delighted, gently patting Lü Meng's back, saying, 'Before, I thought you, this rough fellow, only had military prowess. Now I realize your scholarship is profound, and your views are unique. You are no longer the 'Ah Meng of Wu' you once were!' Lü Meng smiled confidently and said, 'When a scholar has been away for three days, one should look at him with new eyes. How can you still view me with old perspectives?'