Ahmar,the Companion of the Messenger of Allah (ﷺ), narrated to us:
"Weused to feel sorry for the Messenger of Allah (ﷺ) because hetookpains to keep his arms away from his sides when he prostrated." (ES)
English reference (ES): Vol. 1, Book 5, Hadith 886 (ES)
Arabic reference (ES): Book 5, Hadith 936 (ES)