Musnad Ahmad 30:3809

Abu Kamil and Hashim narrated to us, they said: Zuhayr narrated to us, Suhayl narrated to us, from his father, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever sleeps while there is *ghamr* (grease or residue of meat) on his hand and he does not wash it, and something befalls him, then let him blame none but himself."