Sahih Muslim 6483
صحيح مسلم#6483SahihJabir b. 'Abdullah reported Allah's Apostle (ﷺ) as saying one mouth before his death (or something like it):None amongst the created beings who had been living by that time (during the lifetime of Allah's Apostle).... 'Abd al-Rahman has interpreted these words of Allah's Apostle (ﷺ) as: The ages (of the people) would be diminished
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: 44:312