عَنْ عُمَرَ رَضِيَ اللَّهُ عَنْهُ أَنَّهُ قَالَ يَا رَسُولَ اللَّهِ إِنِّي نَذَرْتُ فِي الْجَاهِلِيَّةِ أَنْ أَعْتَكِفَ فِي الْمَسْجِدِ الْحَرَامِ لَيْلَةً فَقَالَ لَهُ فَأَوْفِ بِنَذْرِكَ
It is narrated from Sayyiduna Umar (may Allah be pleased with him) that he said: O Messenger of Allah! In the days of ignorance, I made a vow that I would perform i'tikaf for one night in Masjid al-Haram. The Prophet (peace and blessings be upon him) said: Fulfill your vow.