The overcrowding of the people when the Imam recites As-Sajda
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.
Narrated Ibn `Umar: 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.