(6) باب فِي الرَّجُلِ يَسْمَعُ السَّجْدَةَ وَهُوَ رَاكِبٌ وَفِي غَيْرِ الصَّلاَةِ
Narrated Abdullah ibn Umar:
In the year of Conquest the Messenger of Allah (ﷺ) 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.
Reference: Sunan Abi Dawud 1411
In-book reference: Book 7, Hadith 11
English translation: Book 7, Hadith 1406