Sahih Muslim 6927
صحيح مسلم#6927SahihAbu Dharr reported that Allah's Messenger (ﷺ) said:There is no believing servant who supplicates for his brother behind his back (in his absence) that the Angels do not say: The same be for you too
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: 48:119