Sahih al-Bukhari 1076
Sahih al-Bukhari · Book 17: Prostration During Recital of Qur'an · The overcrowding of the people when the Imam recites As-Sajda
Narrated Ibn `Umar:
حَدَّثَنَا بِشْرُ بْنُ آدَمَ ، قَالَ حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ ، قَالَ أَخْبَرَنَا عُبَيْدُ اللَّهِ ، عَنْ نَافِعٍ ، عَنِ ابْنِ عُمَرَ ، قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم يَقْرَأُ السَّجْدَةَ وَنَحْنُ عِنْدَهُ فَيَسْجُدُ وَنَسْجُدُ مَعَهُ فَنَزْدَحِمُ حَتَّى مَا يَجِدُ أَحَدُنَا لِجَبْهَتِهِ مَوْضِعًا يَسْجُدُ عَلَيْهِ.
When the Prophet (ﷺ) recited Surat As-Sajda and we were with him, he would prostrate and we also would prostrate with him and some of us (because of the heavy rush) would not find a place (for our foreheads) to prostrate on.