Abu Hurairah reported :The Messenger of Allah (ﷺ) said: When anyone amongst you wakes up from sleep at night, he should not put his hand in the utensil until he has washed his hand three times, for he does’ not know where his hand was during the night.
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنِ الأَعْمَشِ، عَنْ أَبِي رَزِينٍ، وَأَبِي، صَالِحٍ عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا قَامَ أَحَدُكُمْ مِنَ اللَّيْلِ فَلاَ يَغْمِسْ يَدَهُ فِي الإِنَاءِ حَتَّى يَغْسِلَهَا ثَلاَثَ مَرَّاتٍ فَإِنَّهُ لاَ يَدْرِي أَيْنَ بَاتَتْ يَدُهُ " .
AbuDaud
Purification (Kitab Al-Taharah) • Hadith 103