Sahih Bukhari
Sahih Bukhari Volume 003, Book 033, Hadith Number 260.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 33. Retiring To a Masjid for Remembrance Of Allah (I'tikaf)
Narated By Abu Huraira : The Prophet used to perform Itikaf every year in the month of Ramadan for ten days, and when it was the year of his death, he stayed in Itikaf for twenty days.