According to Imam Muslim in his Sahih, Anas (may Allah be pleased with him) stated that Allah's Messenger (peace and blessings be upon him) performed four `Umrahs, all during the month of Dhul-Qi`dah except the one he performed along with Hajj (and these are) the `Umrah that he performed from Al-Hudaibiyah or during the time of (the truce of) Hudaibiyah in the month of Dhul-Qi`dah then the `Umrah of the next year in the month of Dhul-Qi`dah, then the `Umrah for which he had started from Ji`ranah, the place where he distributed the spoils of (the battle of) Hunain in the month of Dhul-Qi`dah, and then the `Umrah that he performed along with his Hajj (on the occasion of the Farewell Pilgrimage).
The First `Umrah: According to this narration, Anas (may Allah be pleased with him) counted the `Umrahs performed by Allah's Messenger (peace and blessings be upon him) as four on the basis that the `Umrah of Hudaibiyah (that was performed during the time of the truce of Al-Hudaibiyah) in which the disbelievers prevented Muslims from proceeding to perform it has been counted. That is because the Prophet and the Muslims had intended to perform `Umrah, then they were prevented from fulfilling it and as a result they dissolved their Ihram (i.e. a state of ritual consecration).