It is narrated from Sayyiduna Anas (may Allah be pleased with him), who was one of the Companions of the Prophet (peace and blessings be upon him), that the Messenger of Allah (peace and blessings be upon him) said: "Ride these animals while they are sound, and leave them while they are sound, and do not make them into chairs (that is, do not stay sitting on their backs without need)." This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.