(5) باب الاِعْتِكَافِ لَيْلاً
Narrated Ibn `Umar:
`Umar asked the Prophet (ﷺ) "I vowed in the Pre-Islamic period of ignorance to stay in I`tikaf for one night in Al-Masjid al-Haram." The Prophet (ﷺ) said to him, "Fulfill your vow."
Reference: Sahih al-Bukhari 2032
In-book reference: Book 33, Hadith 7
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 33, Hadith 248