Sahih al-Bukhari 2044
صحيح البخاري#2044SahihNarrated Abu Huraira:The Prophet (ﷺ) used to perform I`tikaf every year in the month of Ramadan for ten days, and when it was the year of his death, he stayed in I`tikaf for twenty days
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 33:19