Sahih Muslim Book 7, Hadith Number 2917.

Chapter : It is permissible to observe Tawaf on the back of a camel or any other riding beast, and to touch the black stone with a stick.

Ibn ‘Abbas (Allah be pleased with him) reported that Allah’s Messenger (may peace be upon him) circumambulated the House on the occasion of the Farewell Pilgrimage on the back of his camel and touched the Corner (of Black Stone) with a stick.