Sahih al-Bukhari 1220
صحيح البخاري#1220SahihNarrated Abu Huraira:It was forbidden to pray with the hands over one's hips
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 21:24