Musannaf Ibn Abi Shayba 3:1833

Abu Bakr narrated to us, he said: Waki’ ibn al-Jarrah narrated to us, from Mis’ar, from Wabarah, who said: I asked Ibn ‘Umar while I was coming from Medina about a man who recites a prostration [verse] while he is upon a riding beast. He said: He gestures.