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كتاب المغازى
64  
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
(50)
Chapter: The encamping place of the Prophet (saws) on the day of the Conquest (of Makkah)
(50)
باب مَنْزِلُ النَّبِيِّ صلى الله عليه وسلم يَوْمَ الْفَتْحِ
Sahih al-Bukhari 4292

Narrated Ibn Abi Laila:

None informed us that he saw the Prophet (ﷺ) offering the Duha (i.e. forenoon) prayer, except Um Hani who mentioned that the Prophet (ﷺ) took a bath in her house on the day of the Conquest (of Mecca) and then offered an eight rak`at prayer. She added, "I never saw the Prophet (ﷺ) offering a lighter prayer than that prayer, but he was performing perfect bowing and prostrations."

حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا شُعْبَةُ، عَنْ عَمْرٍو، عَنِ ابْنِ أَبِي لَيْلَى، مَا أَخْبَرَنَا أَحَدٌ، أَنَّهُ رَأَى النَّبِيَّ صلى الله عليه وسلم يُصَلِّي الضُّحَى غَيْرَ أُمِّ هَانِئٍ، فَإِنَّهَا ذَكَرَتْ أَنَّهُ يَوْمَ فَتْحِ مَكَّةَ اغْتَسَلَ فِي بَيْتِهَا ثُمَّ صَلَّى ثَمَانِيَ رَكَعَاتٍ، قَالَتْ لَمْ أَرَهُ صَلَّى صَلاَةً أَخَفَّ مِنْهَا غَيْرَ أَنَّهُ يُتِمُّ الرُّكُوعَ وَالسُّجُودَ‏.‏
Reference : Sahih al-Bukhari 4292
In-book reference : Book 64, Hadith 325
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 587
  (deprecated numbering scheme)