Musannaf Ibn Abi Shayba 1:1049

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