Chapter 96: Holding Fast to the Qur'an and Sunnah
Narrated Humaid bin 'Abdur-Rahman that he heard Mu' awiya talking to a group of people from Quraish at Al-Madina, and on mentioning Ka' b Al-Ashbar, he said, "He was one of the most truthful of those who used to talk about the people of the Scripture, yet we used to detect certain faults in his information."
Sahih al-Bukhari 7361