"The Messenger of Allah (ﷺ) prohibited riding (while sitting on) Miyathir."

There are narrations on this topic from 'Ali and Mu'awiyah. The Hadith if Al-Bara' is Hasan Sahih. Shu'bah reported similarly from Ash'ath bin Abi Ash-Sha'tha' in the lengthy Hadith.

Jami` at-Tirmidhi Book 24, Hadith 43