Sahih Muslim 351
صحيح مسلم#351SahihAnas b. Malik transmitted it from the Messenger of Allah (ﷺ) that the Great and Glorious Allah said:Verily your people would constantly question about this and that till they would say: Well, it is Allah Who created the creation, but who created Allah?
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: 1:258