Sahih Muslim Book 7, Hadith Number 2918.

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.

Jabir (Allah be pleased with him) reported that Allah’s Messenger (may peace be upon him) circumambulated the House on the back of his riding camel on the occasion of the Farewell Pilgrimage and touched the Stone with his stick so that the people should see him, and he should be conspicuous, and they should be able to ask him (questions pertaining to religion) as the people had crowded round him.