Sahih al-Bukhari 212

Arabic

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 ‏"‏‏.‏

English translation

Narrated `Aisha: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

Reference: Sahih al-Bukhari 212, Book of Ablutions (Wudu'). English translation by Dr. Muhammad Muhsin Khan.