Messenger of Allah, I had taken a vow during the days of Ignorance (Jahiliyya) that I would observe I'tikaf for a night in the Sacred Mosque. He (the Holy Prophet) said: Fulfil your vow.
يَا رَسُولَ اللَّهِ إِنِّي نَذَرْتُ فِي الْجَاهِلِيَّةِ أَنْ أَعْتَكِفَ لَيْلَةً فِي الْمَسْجِدِ الْحَرَامِ قَالَ فَأَوْفِ بِنَذْرِكَ