Musnad Abu Ya'la al-Mawsili 155:133

Abu Hammam narrated to us, Abd al-Rahim ibn Sulayman narrated to us, from Muhammad ibn Amr al-Laythi, from Abu Salamah ibn Abd al-Rahman, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you rises from his sleep, let him pour over his hands from his vessel, for he does not know where his hand spent the night." Qayn al-Ashja'i said: "What if we come to this mortar of yours?" He (the Prophet) said: "I seek refuge in Allah from your evil, O Qayn."