It was narrated from ‘Umar that he had vowed during the days of Ignorance to spend one night in I’tikaf. He asked the Prophet ﷺ about it, so he commanded him to spend it in I’tikaf.  

أَنَّهُ كَانَ عَلَيْهِ نَذْرُ لَيْلَةٍ فِي الْجَاهِلِيَّةِ يَعْتَكِفُهَا فَسَأَلَ النَّبِيَّ ﷺ فَأَمَرَهُ أَنْ يَعْتَكِفَ