when 'Abdullah b. Sinan mentioned a man troubled with doubts in his ablution and his prayers, and claimed that he was a sane man, said, 'What kind of mind does he have if he is obeying Satan?!' [He said] So I said to him, 'And how is he obeying Satan?' So he said, 'Ask him this [misgiving] that he has, where does it come from?' And he shall say to you, 'It is an act of Satan.'