The Book of the Prohibited actions

Riyad as-Salihin · Chapter 338

Prohibition of Placing the hands on the sides during As-Salat (The Prayer)

باب كراهة وضع اليد على الخاصرة في الصلاة

Prayer has a posture of the body that mirrors a posture of the heart. This brief chapter notes one discouraged stance: standing in prayer with a hand resting on the hip. The concern is the attitude such a pose carries, a relaxed, self-satisfied bearing that does not belong before Allah.

What to notice is how closely Islam ties the outward to the inward. Even where one places the hands while standing is shaped so the worshipper looks and feels like a humble servant, not someone standing at ease. The detailed ruling is a matter for scholars; the heart of it is reverence in how we hold ourselves before our Lord.

Hadith 1752

Abu Hurairah (May Allah be pleased with him) said:

عن أبي هريرة رضي الله عنه أن رسول الله صلى الله عليه وسلم‏:‏ نهى عن الخصر في الصلاة‏.‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏‏.‏

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

In plain words

This brief report tells us the believers were told not to stand in prayer with a hand resting on the hip. It guards against a relaxed, self-satisfied posture before Allah.

Reference : Riyad as-Salihin 1752 In-book reference : Book 17, Hadith 242