Riyad as-Salihin

Riyad as-Salihin 1752

Prohibition of Placing the hands on the sides during As-Salat (The Prayer)
Arabic hadith text
عن أبي هريرة رضي الله عنه أن رسول الله صلى الله عليه وسلم‏:‏ نهى عن الخصر في الصلاة‏.‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏‏.‏
Translation
Abu Hurairah (May Allah be pleased with him) said

We are prohibited from placing the hand on the side during As-Salat (the prayer).[Al-Bukhari and Muslim].