Sahih al-Bukhari 212
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · Ablution after sleep. And whoever considers it unnecessary to repeat ablution after dozing once or twice or after nodding once in slumber
Narrated `Aisha:
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ ، قَالَ أَخْبَرَنَا مَالِكٌ ، عَنْ هِشَامٍ ، عَنْ أَبِيهِ ، عَنْ عَائِشَةَ ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِذَا نَعَسَ أَحَدُكُمْ وَهُوَ يُصَلِّي فَلْيَرْقُدْ حَتَّى يَذْهَبَ عَنْهُ النَّوْمُ، فَإِنَّ أَحَدَكُمْ إِذَا صَلَّى وَهُوَ نَاعِسٌ لاَ يَدْرِي لَعَلَّهُ يَسْتَغْفِرُ فَيَسُبَّ نَفْسَهُ " .
Allah's Messenger (ﷺ) said, "If anyone of you feels drowsy while praying he should go to bed (sleep) till his slumber is over because in praying while drowsy one does not know whether one is asking for forgiveness or for a bad thing for oneself."