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كتاب الأذان
10
Call to Prayers (Adhaan)
(41)
Chapter: Can the Imam offer the Salat (prayer) with only those who are present (for the prayer)? And can be deliver a Khutba (religious talk) on Friday if it is raining?
(41)
باب هَلْ يُصَلِّي الإِمَامُ بِمَنْ حَضَرَ وَهَلْ يَخْطُبُ يَوْمَ الْجُمُعَةِ فِي الْمَطَرِ

Narrated Abu Sa`id Al-Khudri:

A cloud came and it rained till the roof started leaking and in those days the roof used to be of the branches of date-palms. Iqama was pronounced and I saw Allah's Messenger (ﷺ)s prostrating in water and mud and even I saw the mark of mud on his forehead.

حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا هِشَامٌ، عَنْ يَحْيَى، عَنْ أَبِي سَلَمَةَ، قَالَ سَأَلْتُ أَبَا سَعِيدٍ الْخُدْرِيَّ فَقَالَ جَاءَتْ سَحَابَةٌ فَمَطَرَتْ حَتَّى سَالَ السَّقْفُ، وَكَانَ مِنْ جَرِيدِ النَّخْلِ، فَأُقِيمَتِ الصَّلاَةُ، فَرَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَسْجُدُ فِي الْمَاءِ وَالطِّينِ، حَتَّى رَأَيْتُ أَثَرَ الطِّينِ فِي جَبْهَتِهِ‏.‏
Reference : Sahih al-Bukhari 669
In-book reference : Book 10, Hadith 63
USC-MSA web (English) reference : Vol. 1, Book 11, Hadith 638
  (deprecated numbering scheme)