Sahih al-Bukhari 1813

Narrated Nafi`: When `Abdullah bin `Umar set out for Mecca with the intentions performing `Umra in the period of afflictions, he said, "If I should be prevented from reaching the Ka`ba, then I would do the same as we did while in the company of Allah's Messenger (ﷺ) ." So, he assumed the Ihram for `Umra since the Prophet (ﷺ) had assumed the Ihram for `Umra in the year of Al-Hudaibiya. Then `Abdullah bin `Umar thought about it and said, "The conditions for both Hajj and `Umra are similar." He then turned towards his companions and said, "The conditions of both Hajj and `Umra are similar and I make you witnesses that I have made the performance of Hajj obligatory for myself along with `Umra." He then performed one Tawaf (between As-Safa and Al-Marwa) for both of them (i.e. Hajj and (`Umra) and considered that to be sufficient for him and offered a Hadi.