Narrated Abu Huraira: The Prophet 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.
Hadith Referenceصحيح البخاري / كتاب الاعتكاف / 2044
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة