Narrated Sahl bin Sad:

The Prophet ﷺ 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 ﷺ 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 ﷺ 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 ﷺ in the (first) row. The Prophet ﷺ 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 ﷺ went forward and led the prayer. (See Hadith No. 295 &
296)

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ أَبِي حَازِمٍ، عَنْ أَبِيهِ، عَنْ سَهْلٍ ـ رضى الله عنه ـ قَالَ خَرَجَ النَّبِيُّ ﷺ يُصْلِحُ بَيْنَ بَنِي عَمْرِو بْنِ عَوْفٍ، وَحَانَتِ الصَّلاَةُ، فَجَاءَ بِلاَلٌ أَبَا بَكْرٍ ـ رضى الله عنهما ـ فَقَالَ حُبِسَ النَّبِيُّ ﷺ فَتَؤُمُّ النَّاسَ قَالَ نَعَمْ إِنْ شِئْتُمْ. فَأَقَامَ بِلاَلٌ الصَّلاَةَ، فَتَقَدَّمَ أَبُو بَكْرٍ ـ رضى الله عنه ـ فَصَلَّى، فَجَاءَ النَّبِيُّ ﷺ 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 ﷺ فِي الصَّفِّ، فَأَشَارَ إِلَيْهِ مَكَانَكَ. فَرَفَعَ أَبُو بَكْرٍ يَدَيْهِ، فَحَمِدَ اللَّهَ، ثُمَّ رَجَعَ الْقَهْقَرَى وَرَاءَهُ وَتَقَدَّمَ النَّبِيُّ ﷺ فَصَلَّى.