ʿUmar asked the Prophet ﷺ "I vowed in the Pre-Islamic period of ignorance to stay in Iʿtikaf for one night in Al-Masjid al-Haram." The Prophet ﷺ said to him, "Fulfill your vow."  

أَنَّ عُمَرَ سَأَلَ النَّبِيَّ ﷺ قَالَ كُنْتُ نَذَرْتُ فِي الْجَاهِلِيَّةِ أَنْ أَعْتَكِفَ لَيْلَةً فِي الْمَسْجِدِ الْحَرَامِ قَالَ فَأَوْفِ بِنَذْرِكَ