It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to observe i'tikaf during the last and middle ten days of Ramadan. When the Messenger of Allah (peace and blessings be upon him) passed away, he was observing i'tikaf for twenty days.
Hadith Referenceالفتح الربانی / كتاب الصيام / 3999
Hadith Gradingمحدثین:صحیح
Hadith Takhrij«اخرجه البخاري: 2044، 4998، (انظر مسند أحمد ترقيم الرسالة: 9212 ترقیم بيت الأفكار الدولية: 9201»
Brief Explanation
Benefits: … There may be several reasons for the twenty days of i‘tikaf (spiritual retreat) mentioned in this blessed hadith:
(1) The Prophet sallallahu alayhi wa sallam increased the duration of i‘tikaf in the latter part of his life in order to accumulate more goodness and virtue.
(2) It is possible that, according to the second or third hadith of this chapter, the compensatory i‘tikaf (qada) occurred during these very days.
(3) In every Ramadan, Jibril alayhis salam would review the Qur’an with the Prophet sallallahu alayhi wa sallam once, but in the year of his passing, this review was done twice. It is possible that, due to this, the Prophet sallallahu alayhi wa sallam performed i‘tikaf for twenty days.
Whichever meaning is adopted, the established ruling remains that making up (qada) for i‘tikaf is permissible, and performing i‘tikaf for more than ten days is also permissible.