(17) باب الْخَصْرِ فِي الصَّلاَةِ
Narrated Abu Huraira:
It was forbidden to keep the hands on the hips during the prayer. (This is narrated by Abu Huraira from the Prophet.)
Reference: Sahih al-Bukhari 1219
In-book reference: Book 21, Hadith 23
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 22, Hadith 310