Sahih Muslim 1552
صحيح مسلم#1552SahihAnas b. Malik reported that the Messenger of Allah (ﷺ) observed Qunut for one month Invoking curse upon Ri'l, Dhakwan, 'Usayya. those who disobeyed Allah and His Messenger (ﷺ)
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: 5:385