Sahih al-Bukhari 1075
Sahih al-Bukhari · Book 17: Prostration During Recital of Qur'an · Whoever prostrated with the prostration of the reciter
Narrated Ibn `Umar:
حَدَّثَنَا مُسَدَّدٌ ، قَالَ حَدَّثَنَا يَحْيَى ، عَنْ عُبَيْدِ اللَّهِ ، قَالَ حَدَّثَنِي نَافِعٌ ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم يَقْرَأُ عَلَيْنَا السُّورَةَ فِيهَا السَّجْدَةُ، فَيَسْجُدُ وَنَسْجُدُ، حَتَّى مَا يَجِدُ أَحَدُنَا مَوْضِعَ جَبْهَتِهِ.
When the Prophet (ﷺ) recited a Sura that contained the prostration he would prostrate and we would do the same and some of us (because of the heavy rush) could not find a place for prostration.