Narrated Nafi: Abdullah bin Umar set out for Umra during the period of afflictions, and he said, "If I should be stopped from visiting the Kaba, I will do what we did when we were with Allah's Apostle." He assumed Ihram for 'Umra in the year of AlHudaibiya.
— Sahih Bukhari, Volume 5, Book 59: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi), Hadith #497