Sahih Muslim 196
صحيح مسلم#196SahihIt is narrated on the authority of Tamim ad-Dari that the Prophet (ﷺ) said:"The Religion is sincerity." We said, "To whom?" He said "To Allah, to His Book, To His Messenger, and to the leaders of the Muslims and their masses
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: 1:103