It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Beware of making the backs of your animals into pulpits, for Allah Almighty says that He has subjected them to you so that they 'carry your loads to a land you could not reach except with great hardship to yourselves' [Surah al-Nahl: 7], and Allah has made the earth for you, so fulfil your needs upon it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10335
Sahl bin Mu'adh bin Anas narrates from his father (may Allah be pleased with him), who was one of the Companions of the Prophet (peace and blessings be upon him), that the Prophet (peace and blessings be upon him) said: "Ride these animals while they are sound, and return them sound, and do not make them into thrones or chairs."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10336