Musannaf Ibn Abi Shayba 35:192

Abu Khalid al-Ahmar narrated to us, from Hisham, from Muhammad ibn Sirin, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you wakes up at night, he should not dip his hand into the vessel until he has washed it."