Sunan Ibn Majah — Establishing the Prayer and the Sunnah Regarding Them — Hadith No: 1284
Translation
It was narrated that Isma’il bin Abu Khalid said:“I saw Abu Kahil, and he was a Companions, and my brother narrated to me that he said: ‘I saw the Prophet (ﷺ) delivering the sermon atop his she-camel, and an Ethiopian was holding onto its reins.’”