Sahih Muslim 1581
صحيح مسلم#1581SahihAnas reported:The Messenger of Allah (ﷺ) said four rak'ahs in the noon prayer while at Medina, but he offered two rak'ahs in the afternoon prayer at Dhu'l-Hulaifa
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: 6:12