Musnad Ahmad 31:359

Hashim narrated to us, he said: Shu'bah narrated to us, from 'Amr ibn Dinar, from Sulayman al-Yashkuri, from Abu Sa'id al-Khudri, that he said: "Regarding the *wahm* (doubt/misconception), one should seek [the truth]." A man said to him: "From the Prophet, may Allah bless him and grant him peace?" He said: "As far as I know."