Musannaf Ibn Abi Shayba 3:3481

Waki’ narrated to us, from Isma’il bin Abi Khalid, from his brother, from Abu Kahil, who said: I saw the Prophet, may Allah bless him and grant him peace, delivering a sermon while upon a she-camel that was tied with a girth, and an Abyssinian was holding its halter.