From Sahih Bukhari (Hadith 1516):
Narrated 'Aishah:The Prophet (ﷺ) sent my brother, 'Abdur Rahman with me to Tan'im for the 'Umra, and he made me ride on the packsaddle (of a camel). 'Umar said, "Be ready to travel for Hajj as it (Hajj) is one of the two kind of Jihad
Reference: Bukhari 1516