Musannaf Ibn Abi Shayba 3:2154

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Ash'ath ibn Abi al-Sha'tha', from his father, from Masruq, from 'Aishah, she said: I asked the Messenger of Allah, may Allah bless him and grant him peace, about looking around during prayer. He said: "It is a snatching that the Shaytan snatches from the servant's prayer."