Tsai Yu, also known as Tsai Tsu-wo(子我), was one of Confucius' students. He was born in the kingdom of Lu and was later classified by Confucius in the group of people who were good at speech. Once he asked Confucius. "If somebody informs a benevolent person that a man fell into a well, should the benevolent descend into the well to save him?" Confucius replied, "Not necessarily. Anyone might believe what another says and run to help, but he himself will not be trapped. He may be tricked by someone's logic, but that does not mean he will be fooled into doing something stupid himself.
Reference:《THE BRIEF BIOGRAPHIES OF THE SAINTS AND SAGES ARE IN THE TA CHENG HALL OF THE CONFUCIUS TEMPLE》published by Taipei Confucius Temple Governing Board