Source: "The Analects of Confucius" Yan Yuan: "A gentleman treats others with courtesy, and all men are brothers within the four seas."

During the Spring and Autumn Period, Sima Niu, a disciple of Confucius, asked Confucius how to be a gentleman. Confucius said that a gentleman is not sad, not afraid, and often introspects. After seeing Xia Zi, Sima Niu said sadly that he had no brothers. Xia Zi comforted him that a gentleman's attitude towards people is respectful and polite, so there are brothers everywhere in the world.