Sahih Muslim 1475
صحيح مسلم#1475SahihAbu Huraira reported Allah's Messenger (ﷺ) as saying:Prayer said in a congregation is equivalent to twenty-five (prayers) as compared with the prayer said by a single person
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: 5:308