al-Hasan bin Musa al-'Ashayb الحسن بن موسى الأشيب · The Book on Hajj

Ibn Umar was asked: In which month did the Messenger of Allah perform Umrah? He said: 'During Rajab.' So Aishah said: 'The Messenger of Allah did not perform Umrah except that he was with him - meaning Ibn Umar - and he did not ever perform Umrah in the month of Rajab.'"