Retiring to a Mosque for Remembrance of Allah (I'tikaf)
Bukhari :: Book 3 :: Volume 33 :: Hadith 258
Narrated Abdullah bin Umar:
'Umar bin Al-Khattab said, "O Allah's Apostle! I vowed in the Pre-lslamic period to perform Itikaf in Al-Masjid-al-Haram for one night." The Prophet said, "Fulfill your vow." So, he performed Itikaf for one night.
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