Sahih al-Bukhari 1220
Book 21: Actions while Praying · Narrated by Abu Huraira
Arabic
حَدَّثَنَا عَمْرُو بْنُ عَلِيٍّ، حَدَّثَنَا يَحْيَى، حَدَّثَنَا هِشَامٌ، حَدَّثَنَا مُحَمَّدٌ، عَنْ أَبِي هُرَيْرَةَ، رضى الله عنه قَالَ نُهِيَ أَنْ يُصَلِّيَ الرَّجُلُ مُخْتَصِرًا.
English translation
Narrated Abu Huraira:It was forbidden to pray with the hands over one's hips
Reference: Sahih al-Bukhari 1220, Book of Actions while Praying. English translation by Dr. Muhammad Muhsin Khan.