Sahih Bukhari

Narrated `Abdullah bin `Umar:`Umar bin Al-Khattab said, ""O Allah's Messenger (ﷺ)! I vowed in the Pre-Islamic period to perform I`tikaf in Al-Masjid-al-Haram for one night."" The Prophet (ﷺ) said, ""Fulfill your vow."" So, he performed I`tikaf for one night