Musnad Abu Ya'la al-Mawsili 245:19

Ibrahim ibn al-Husayn al-Antaki narrated to us, Baqiyyah ibn al-Walid narrated to us, from Abu Bakr ibn Abi Maryam, from Atiyyah ibn Qays, who said: I heard Mu'awiyah ibn Abi Sufyan saying: I heard the Messenger of Allah (peace and blessings of Allah be upon him) saying: "The eye is the tie of the anus. So when the eye sleeps, the tie is released."