This famous saying should come from the Teacher's Theory written by Han Yu in the Tang Dynasty, in which the original text reads: "Before I was born, my knowledge of Tao was also prior to mine, so I learned from it; After I was born, I heard the Tao first, so I learned from it. " It means that people with high or low status, old or young, should be our teachers as long as they have knowledge and ability. We learn from them because they all have knowledge and skills that we don't know.