Sahih Muslim Book - 5, Hadith - 1295

حَدَّثَنِى زُهَيْرُ بْنُ حَرْبٍ وَعُبَيْدُ اللَّهِ بْنُ سَعِيدٍ وَمُحَمَّدُ بْنُ الْمُثَنَّى كُلُّهُمْ عَنْ يَحْيَى الْقَطَّانِ - قَالَ زُهَيْرٌ حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ - عَنْ عُبَيْدِ اللَّهِ قَالَ أَخْبَرَنِى نَافِعٌ عَنِ ابْنِ عُمَرَ أَنَّ النَّبِىَّ -صلى الله عليه وسلم- كَانَ يَقْرَأُ الْقُرْآنَ فَيَقْرَأُ سُورَةً فِيهَا سَجْدَةٌ فَيَسْجُدُ وَنَسْجُدُ مَعَهُ حَتَّى مَا يَجِدُ بَعْضُنَا مَوْضِعًا لِمَكَانِ جَبْهَتِهِ.

It was narrated from Ibn 'Umar that the Prophet (s.a.w) used to recite the Qur'an, and when he recited a Surah in which a prostration was required, he would prostrate, and we would prostrate with him, until some of us could not find any spot for his forehead.