Musannaf Ibn Abi Shayba 17:1376

'Isa ibn Yunus narrated to us, from 'Abd al-Rahman ibn Yazid ibn Jabir, from Makhul, that he used to dislike sleeping after the 'Asr [prayer]. And he said: "It is feared for the one who does so that he may be afflicted by *al-waswas* (insanity or obsessive whispers)."