Sahih al-Bukhari
Sahih al-Bukhari 213
Ablution after sleep. And whoever considers it unnecessary to repeat ablution after dozing once or twice or after nodding once in slumber
Arabic hadith text
حَدَّثَنَا أَبُو مَعْمَرٍ، قَالَ حَدَّثَنَا عَبْدُ الْوَارِثِ، حَدَّثَنَا أَيُّوبُ، عَنْ أَبِي قِلاَبَةَ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ "إِذَا نَعَسَ أَحَدُكُمْ فِي الصَّلاَةِ فَلْيَنَمْ حَتَّى يَعْلَمَ مَا يَقْرَأُ "
Translation
Narrated Anas
The Prophet (ﷺ) said, "If anyone of you feels drowsy while praying, he should sleep till he understands what he is saying (reciting).