Sahih Muslim 1218
صحيح مسلم#1218SahihAbu Huraira reported from the Messenger of Allah (ﷺ) that he forbade keeping one's hand on one's waist while praying, and in the narration of Abu Bakr (the words are):The Messenger of Allah (ﷺ) forbade to do so
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 5:58