Hadith 817:2
Affan narrated to us, Abbad bin Rashid narrated to us, Al-Hasan narrated to us, Ahmar, a companion of the Messenger of Allah (may Allah bless him and grant him peace), narrated to me, saying: "We used to feel pity for the Messenger of Allah (may Allah bless him and grant him peace) because of how he would keep his arms away from his sides when he prostrated."
حدثنا عفان، حدثنا عباد بن راشد، حدثنا الحسن، حدثني أحمر، صاحب رسول الله صلى الله عليه وسلم قال: " كنا لنأوي لرسول الله صلى الله عليه وسلم مما يجافي بيديه عن جنبيه إذا سجد "