Sahih Bukhari | Volume 6 | Hadith Number 520

Narrated by Abu-Huraira
Gabriel used to repeat the recitation of the Qur'an with the Prophet once a year, but he repeated it twice with him in the year he died. The Prophet used to stay in I'tikaf for ten days every year (in the month of Ramadan), but in the year of his death, he stayed in I'tikaf for twenty days.