(79) باب أَيْنَ يَكُونُ الاِعْتِكَافُ
Abu Hurairah said:
The Prophet (ﷺ) used to observe I'tikaf during ten days of Ramadan every year. But when the year in which he died, he observed I'tikaf for twenty days.
Reference: Sunan Abi Dawud 2466
In-book reference: Book 14, Hadith 154
English translation: Book 13, Hadith 2460