Sahih Muslim 943
صحيح مسلم#943SahihA'isha reported:The Messenger of Allah (ﷺ) ordered Abu Bakr that he should lead people in prayer during his illness, and he led them in prayer. `Urwa said: The Messenger of Allah (ﷺ) felt relief and went (to the mosque) and Abu Bakr was leading the people in prayer. When Abu Bakr saw him he began to withdraw, but the Messenger of Allah (ﷺ) signaled him to remain where he was. The Messenger of Allah (ﷺ) sat opposite to Abu Bakr by his side. Abu Bakr said prayer following the prayer of the Messenger of Allah (ﷺ), and the people said prayer following the prayer of Abu Bakr
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: 4:105