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].