What did the Prophet Muhammad (saw) tell Umar when Umar revealed he had made a vow in the Pre-Islamic Period of Ignorance to perform I'tikaf for one night in Al-Masjid-al-Haram?
 Narrated Ibn `Umar:                     `Umar said "O Allah's Apostle! I vowed to perform I`tikaf for one night in Al-Masjid-al-Haram, during the Pre-Islamic Period of ignorance (before embracing Islam). "The Prophet said, "Fulfill your vow." Ibn `Umar said to the lady, "Pray on her behalf." Ibn `Abbas said the same.