Zai Yu 宰予 (522-458 BCE), courtesy name Zai Ziwo 宰子我, also called Zai Wo 宰我, was one of the ten wise disciples of Confucius (Kong men shi zhe 孔門十哲). He was 29 years younger than Confucius and was famous for his eloquence. He was therefore used by Confucius as his "voice" and sent as a kind of diplomat to the states of Qi 齊 and Chu 楚.
Zai Yu had a vivid and deep-going thought and loved to ask questions to the Master. He was the only one of Confucius' scholars who dared disputing with the teacher. For instance, he criticized the long period of three years of mourning advocated by Confucius, with the argument that "if the superior man abstains for three years from the observances of propriety and music, those will quite be lost and ruined." Yet Confucius countered that only one year of mourning was not sufficient to express the right way of filial piety towards one's father.
Another dispute between Ziwo and Confucius dealt with a benevolent man who has fallen into a well and threatened to drown. Would another benevolent man go after him into the well to rescue him, likewise facing the danger of dying? Confucius answered that even a benevolent man would not go down to rescue him. "He may be made to go to the well, but cannot be made to go down into it. He may be imposed upon, but he cannot be befooled."
Once, Zai Yu being asleep during the daytime, the Master said: "Rotten wood cannot be carved, and a wall of dirty earth will not reveice the throwel." It was important for Confucius that speech and conduct corresponded, which was not the case with Zai Yu.
During the reign of Emperor Xuanzong 唐玄宗 (r. 712-755) of the Tang dynasty, Zai Yu was posthumously bestowed the honorific title of Marquis of Qi 齊侯, and during the Song period 宋 (960-1279) he became venerated as Duke of Linzi 臨菑公 or Duke of Qi 齊公.
According to the history Shiji 史記, a person called Ziwo became a Grand Master (dafu 大夫) in Linzi 臨菑, the capital of Qi. He participated in Tian Chang's 田常 rebellion against the house of Qi and was killed by Chen Huan 陳恒 in the course of this event. Yet the Tang period 唐 (618-907) scholar Sima Zhen 司馬貞 doubted that the person Ziwo in this event was identical with the Confucian disciple. He assumed that the rebel was no one else than Kan Zhi 闞止, who also bore the courtesy name of Ziwo, and not Zai Yu.