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كتاب الأذان
10
Call to Prayers (Adhaan)
(48)
Chapter: If somebody is leading the Salat (prayer) and (in the meanwhile) the first (usual) Imam comes, the Salat is valid whether the former retreats or does not retreat
(48)
باب مَنْ دَخَلَ لِيَؤُمَّ النَّاسَ فَجَاءَ الإِمَامُ الأَوَّلُ فَتَأَخَّرَ الأَوَّلُ أَوْ لَمْ يَتَأَخَّرْ جَازَتْ صَلاَتُهُ‏
فِيهِ عَائِشَةُ عَنِ النَّبِيِّ صلى الله عليه وسلم
Sahih al-Bukhari 684

Narrated Sahl bin Sa`d As-Sa`idi:

Allah's Messenger (ﷺ) went to establish peace among Bani `Amr bin `Auf. In the meantime the time of prayer was due and the Mu'adh-dhin went to Abu Bakr and said, "Will you lead the prayer, so that I may pronounce the Iqama?" Abu Bakr replied in the affirmative and led the prayer. Allah's Messenger (ﷺ) came while the people were still praying and he entered the rows of the praying people till he stood in the (first row). The people clapped their hands. Abu Bakr never glanced sideways in his prayer but when the people continued clapping, Abu Bakr looked and saw Allah's Messenger (ﷺ). Allah's Messenger (ﷺ) beckoned him to stay at his place. Abu Bakr raised his hands and thanked Allah for that order of Allah's Messenger (ﷺ) and then he retreated till he reached the first row. Allah's Messenger (ﷺ) went forward and led the prayer. When Allah's Messenger (ﷺ) finished the prayer, he said, "O Abu Bakr! What prevented you from staying when I ordered you to do so?" Abu Bakr replied, "How can Ibn Abi Quhafa (Abu Bakr) dare to lead the prayer in the presence of Allah's Messenger (ﷺ)?" Then Allah's Messenger (ﷺ) said, "Why did you clap so much? If something happens to anyone during his prayer he should say Subhan Allah. If he says so he will be attended to, for clapping is for women."

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنْ أَبِي حَازِمِ بْنِ دِينَارٍ، عَنْ سَهْلِ بْنِ سَعْدٍ السَّاعِدِيِّ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم ذَهَبَ إِلَى بَنِي عَمْرِو بْنِ عَوْفٍ لِيُصْلِحَ بَيْنَهُمْ فَحَانَتِ الصَّلاَةُ فَجَاءَ الْمُؤَذِّنُ إِلَى أَبِي بَكْرٍ فَقَالَ أَتُصَلِّي لِلنَّاسِ فَأُقِيمَ قَالَ نَعَمْ‏.‏ فَصَلَّى أَبُو بَكْرٍ، فَجَاءَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَالنَّاسُ فِي الصَّلاَةِ، فَتَخَلَّصَ حَتَّى وَقَفَ فِي الصَّفِّ، فَصَفَّقَ النَّاسُ ـ وَكَانَ أَبُو بَكْرٍ لاَ يَلْتَفِتُ فِي صَلاَتِهِ ـ فَلَمَّا أَكْثَرَ النَّاسُ التَّصْفِيقَ الْتَفَتَ فَرَأَى رَسُولَ اللَّهِ صلى الله عليه وسلم، فَأَشَارَ إِلَيْهِ رَسُولُ اللَّهِ صلى الله عليه وسلم أَنِ امْكُثْ مَكَانَكَ، فَرَفَعَ أَبُو بَكْرٍ ـ رضى الله عنه ـ يَدَيْهِ، فَحَمِدَ اللَّهَ عَلَى مَا أَمَرَهُ بِهِ رَسُولُ اللَّهِ صلى الله عليه وسلم مِنْ ذَلِكَ، ثُمَّ اسْتَأْخَرَ أَبُو بَكْرٍ حَتَّى اسْتَوَى فِي الصَّفِّ، وَتَقَدَّمَ رَسُولُ اللَّهِ صلى الله عليه وسلم فَصَلَّى، فَلَمَّا انْصَرَفَ قَالَ ‏"‏ يَا أَبَا بَكْرٍ مَا مَنَعَكَ أَنْ تَثْبُتَ إِذْ أَمَرْتُكَ ‏"‏‏.‏ فَقَالَ أَبُو بَكْرٍ مَا كَانَ لاِبْنِ أَبِي قُحَافَةَ أَنْ يُصَلِّيَ بَيْنَ يَدَىْ رَسُولِ اللَّهِ صلى الله عليه وسلم‏.‏ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ مَا لِي رَأَيْتُكُمْ أَكْثَرْتُمُ التَّصْفِيقَ مَنْ رَابَهُ شَىْءٌ فِي صَلاَتِهِ فَلْيُسَبِّحْ، فَإِنَّهُ إِذَا سَبَّحَ الْتُفِتَ إِلَيْهِ، وَإِنَّمَا التَّصْفِيقُ لِلنِّسَاءِ ‏"‏‏.‏
Reference : Sahih al-Bukhari 684
In-book reference : Book 10, Hadith 78
USC-MSA web (English) reference : Vol. 1, Book 11, Hadith 652
  (deprecated numbering scheme)