Sahih Muslim 2721
صحيح مسلم#2721SahihA'isha, the Mother of the Believers (Allah be pleased with her), reported that the Messenger of Allah (ﷺ) used to fast (so continuously) that we said that he would not break, and did not fast at all till we said that he would not fast. And I did not see the Messenger of Allah (ﷺ) completing the fast of a month, but that of Ramadan, and I did not see him fasting more in any other month than that of Sha'ban
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: 13:227