Hadith
حَدَّثَنَا مُحَمَّدُ بْنُ مُقَاتِلٍ أَبُو الْحَسَنِ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ عُمَرَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ عُمَرَ، قَالَ يَا رَسُولَ اللَّهِ إِنِّي نَذَرْتُ فِي الْجَاهِلِيَّةِ أَنْ أَعْتَكِفَ لَيْلَةً فِي الْمَسْجِدِ الْحَرَامِ. قَالَ " أَوْفِ بِنَذْرِكَ ".
Narrated Ibn `Umar:`Umar said "O Allah's Messenger (ﷺ)! I vowed to perform I`tikaf for one night in Al-Masjid-al-Haram, during the Pre-Islamic Period of ignorance (before embracing Islam). "The Prophet (ﷺ) said, "Fulfill your vow." Ibn `Umar said to the lady, "Pray on her behalf." Ibn `Abbas said the same
Sahih
Sahih al-Bukhari 6697 ·Book 83, Hadith 74·Also available on sunnah.com·