Musannaf Ibn Abi Shayba 1:1047

Abu Bakr narrated to us, he said: Abu Mu'awiyah narrated to us, from al-A'mash, from Abu Razin, from Abu Hurayrah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you wakes up at night, let him not dip his hand into the vessel until he has washed it three times, for he does not know where his hand spent the night."