On a certain occasion the Prophet (s.a.a.w.) was travelling on his camel over hilly terrain with a disciple, Uqba Bin Aamir. After going some distance, he asked Uqba to ride the camel, but Uqba thought this would be showing disrespect to the Prophet (s.a.a.w.). But the Prophet (s.a.a.w.) insisted and he had to comply. The Prophet (s.a.a.w.) himself walked on foot as he did not want to put too much load on the animal. [Nasai]
(2:83) Remember that We made a solemn covenant with the children of Israel to this effect: worship none save Allah: be good to your parents, to your relatives, to the orphans and to the helpless; speak aright with the people: establish the Salat and pay the Zakat. But with the exception of a few, you all slid back from it and are paying no heed to it even now.