Prayer (Kitab Al-Salat): Prostration while reciting the Qur'an
Dawud :: Book 7 : Hadith 1406
Narrated Abdullah ibn Umar:
In the year of Conquest the Apostle of Allah (peace_be_upon_him) recited a verse at which a prostration should be made and all the people prostrated themselves. Some were mounted, and some were prostrating themselves on the ground, and those who were mounted prostrated themselves on their hands.