Ibn 'Umar (May Allah be pleased with them) said:
The Messenger of Allah (ﷺ) prohibited riding a camel which eats dung, or animal or human waste.[Abu Dawud]. (JA)
App reference (JA): Book 18, Hadith 182 (JA)
Arabic/English book reference (JA): Book 18, Hadith 1692 (JA)