Scared by Zi Yu's ugly look somewhat,Confucius was quite reluctant at first, but Zi Yu entreated Confucius to accept him and eventually Confucius consented.
Zi Yu wanted to overcome Confucius' initial bias, so he was a model student. He did more than was required of him to in his studies. At the end of three years, because of his diligence, he exceeded his classmates in his moral and academic accomplishments.
Zi Yu moved to the State of Wu after completing his studies and founded an academy based upon Confucian principles. The school flourished and its influence was felt far and wide.
Naturally, Confucius was now euphoric about the student of whom he initially judged by appearance. Confucius admitted that his first assessment of Zi Yu was flawed. “Selecting talents only by their appearance, I have done injustice to Zi Yu.”
Today in China, people cite Confucius' words Yi Mao Qu Ren(以貌取人) to underscore that one is in error if they judge talents on the basis of one’s physical appearance. It is basically equal to the English proverb"judge a book by its cover".