Mishkat al-Masabih 1032
He said:
God’s Messenger used to recite the Qur'an to us, and when he came to a place where a prostration should be made he said “God is most great” and prostrated himself, and we prostrated ourselves along with him. 

Abu Dawud transmitted it.
وَعنهُ: أَنه كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقْرَأُ عَلَيْنَا الْقُرْآنَ فَإِذَا مَرَّ بِالسَّجْدَةِ كَبَّرَ وَسجد وسجدنا مَعَه. رَوَاهُ أَبُو دَاوُد