Sahih Bukhari Volume 2, Book 21, Hadith 1202

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ أَبِي حَازِمٍ، عَنْ أَبِيهِ، عَنْ سَهْلٍ ـ رضى الله عنه ـ قَالَ خَرَجَ النَّبِيُّ صلى الله عليه وسلم يُصْلِحُ بَيْنَ بَنِي عَمْرِو بْنِ عَوْفٍ، وَحَانَتِ الصَّلاَةُ، فَجَاءَ بِلاَلٌ أَبَا بَكْرٍ ـ رضى الله عنهما ـ فَقَالَ حُبِسَ النَّبِيُّ صلى الله عليه وسلم فَتَؤُمُّ النَّاسَ قَالَ نَعَمْ إِنْ شِئْتُمْ‏.‏ فَأَقَامَ بِلاَلٌ الصَّلاَةَ، فَتَقَدَّمَ أَبُو بَكْرٍ ـ رضى الله عنه ـ فَصَلَّى، فَجَاءَ النَّبِيُّ صلى الله عليه وسلم يَمْشِي فِي الصُّفُوفِ يَشُقُّهَا شَقًّا حَتَّى قَامَ فِي الصَّفِّ الأَوَّلِ، فَأَخَذَ النَّاسُ بِالتَّصْفِيحِ‏.‏ قَالَ سَهْلٌ هَلْ تَدْرُونَ مَا التَّصْفِيحُ هُوَ التَّصْفِيقُ‏.‏ وَكَانَ أَبُو بَكْرٍ ـ رضى الله عنه ـ لاَ يَلْتَفِتُ فِي صَلاَتِهِ، فَلَمَّا أَكْثَرُوا الْتَفَتَ فَإِذَا النَّبِيُّ صلى الله عليه وسلم فِي الصَّفِّ، فَأَشَارَ إِلَيْهِ مَكَانَكَ‏.‏ فَرَفَعَ أَبُو بَكْرٍ يَدَيْهِ، فَحَمِدَ اللَّهَ، ثُمَّ رَجَعَ الْقَهْقَرَى وَرَاءَهُ وَتَقَدَّمَ النَّبِيُّ صلى الله عليه وسلم فَصَلَّى

Narrated By Sahl bin Sad : The Prophet went out to affect a reconciliation between the tribes of Bani 'Amr bin 'Auf and the time of the prayer became due; Bilal went to Abu Bakr and said, "The Prophet is detained. Will you lead the people in the prayer?" Abu Bakr replied, "Yes, if you wish." So Bilal pronounced the Iqama and Abu Bakr led the prayer. In the meantime the Prophet came crossing the rows (of the praying people) till he stood in the first row and the people started clapping. Abu Bakr never looked hither and thither during the prayer but when the people clapped too much, he looked back and saw the Prophet in the (first) row. The Prophet waved him to remain at his place, but Abu Bakr raised both his hands and sent praises to Allah and then retreated and the Prophet went forward and led the prayer.