Sunan Ibn Majah, Chapter: The Chapters of Purification and its Sunnah

"The Messenger of Allah (saw) said: 'When anyone of you gets up from sleep and wants to perform ablution, he should not put his hand into the vessel he used for ablution until he has washed it, because he does not know where his hand spent the night or where he put it.'" [(One of the narrators) Abu Ishaq said: "What is correct is that it is narrated from Jabir, from Abu Hurairah."] (Hasan)