Who is Tseng Tzu from The Analects and what is their importance?

Tseng Tzu is a disciple of Confucius, and who plays a prominent part in early Confucianism. He is mentioned in the Mencius and the Hsun tzu and other works. Confucius describes him as slow but with great dedication. He is one of a group of four disciples that deserve the title master. Filial duty is associated with him in the Analects. He quotes Confucius that no man realizes himself fully until he mourns for his parents. He is conscientious by his own personal daily examination of whether he does his best, if he remains trustworthy in what he says and whether he recommends to anyone else what he does not try himself.