ENOfficial
It was narrated from Abu Hurairah that the Prophet (ﷺ) said: "When any one of you wakes from sleep, let him not dip his hand in (the water he uses for) his Wudu' until he has washed it three times, for none of you knows where his hand spent the night."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ " إِذَا اسْتَيْقَظَ أَحَدُكُمْ مِنْ نَوْمِهِ فَلاَ يَغْمِسْ يَدَهُ فِي وَضُوئِهِ حَتَّى يَغْسِلَهَا ثَلاَثًا فَإِنَّ أَحَدَكُمْ لاَ يَدْرِي أَيْنَ بَاتَتْ يَدُهُ " .
sunnah.com