Musnad Ahmad 132:38

Hassan narrated to us, Ibn Lahi'ah narrated to us, Zabban narrated to us, from Sahl ibn Mu'adh, from his father, from the Messenger of Allah (peace and blessings of Allah be upon him), that he passed by a people while they were standing upon their beasts and riding animals. The Messenger of Allah (peace and blessings of Allah be upon him) said to them: "Ride them while they are safe, and leave them while they are safe. Do not take them as chairs for your conversations in the roads and the marketplaces. For many a ridden beast is better than its rider, and it is more in remembrance of Allah the Exalted than him."