Musnad Ahmad 30:1844

Muhammad ibn Ja‘far narrated to us, Muhammad ibn ‘Amr narrated to us, from Abu Salamah, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you wakes up from his sleep, let him pour over his hands from his vessel three times, for he does not know where his hand spent the night." Qays al-Ashja‘i said: "O Abu Hurairah, what if your *mihras* (large stone mortar) comes?" He said: "I seek refuge in Allah from your polytheism, O Qays."