Sahih al-Bukhari, Hadith 4998 ⓘ
Narrated 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.
حَدَّثَنَا خَالِدُ بْنُ يَزِيدَ، حَدَّثَنَا أَبُو بَكْرٍ، عَنْ أَبِي حَصِينٍ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ كَانَ يَعْرِضُ عَلَى النَّبِيِّ صلى الله عليه وسلم الْقُرْآنَ كُلَّ عَامٍ مَرَّةً، فَعَرَضَ عَلَيْهِ مَرَّتَيْنِ فِي الْعَامِ الَّذِي قُبِضَ، وَكَانَ يَعْتَكِفُ كُلَّ عَامٍ عَشْرًا فَاعْتَكَفَ عِشْرِينَ فِي الْعَامِ الَّذِي قُبِضَ {فِيهِ}
also referenced under: Book 66, Hadith 20 (In-Book) & Volume 6, Book 61, Hadith 520 (USC-MSA)