What did the Prophet Muhammad (peace be upon him) say to `Umar when he asked about his vow in the Pre-Islamic period of ignorance to stay in I`tikaf for one night in Al-Masjid al-Haram ?
 Narrated Ibn `Umar:                     `Umar asked the Prophet "I vowed in the Pre-Islamic period of ignorance to stay in I`tikaf for one night in Al-Masjid al-Haram." The Prophet said to him, "Fulfill your vow."