Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.147A.
Section : I’tikaf, its legitimacy.
All scholars agree on its legitimacy. The Prophet would perform i’tikaf for ten days every Ramadan. In the year that he died, he performed it for twenty days. This is related by alBukhari, Abu Dawud, and ibn-Majah. The Prophet’s companions and wives performed i’tikaf with him and continued to do so after his death. Even though it is an act which is done to get closer to Allah, there is no sound hadith concerning its merits. Abu Dawud states: “I said to Ahmad, ‘Are you aware of anything concerning the virtues of i’tikaf?’ He answered: ‘No, except for some weak [reports].’ “