It is narrated from Amir al-Mu'minin Sayyiduna Umar bin Khattab (may Allah be pleased with him) that he asked the Noble Prophet (peace and blessings be upon him): "In the days of ignorance, I made a vow that I would perform i'tikaf for one night in the Ka'bah (so should I fulfill this vow or not?)" The Prophet (peace and blessings be upon him) said: "Fulfill your vow."