Sunan Ibn Majah, Book 1, Hadith 427 (In-Book) ⓘ

It was narrated that Jabir said: "The Messenger of Allah said: 'When anyone of oyu 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."]

حَدَّثَنَا إِسْمَاعِيلُ بْنُ تَوْبَةَ، حَدَّثَنَا زِيَادُ بْنُ عَبْدِ اللَّهِ الْبَكَّائِيُّ، عَنْ عَبْدِ الْمَلِكِ بْنِ أَبِي سُلَيْمَانَ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏ "‏ إِذَا قَامَ أَحَدُكُمْ مِنَ النَّوْمِ فَأَرَادَ أَنْ يَتَوَضَّأَ فَلاَ يُدْخِلْ يَدَهُ فِي وَضُوئِهِ حَتَّى يَغْسِلَهَا فَإِنَّهُ لاَ يَدْرِي أَيْنَ بَاتَتْ يَدُهُ وَلاَ عَلَى مَا وَضَعَهَا ‏" ‏ ‏.‏