Sunan Abi Dawud, Book 14, Hadith 2551 (USC-MSA) ⓘ
Narrated Abdullah ibn Umar: It has been prohibited to ride the beast which eats dung.
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ أَيُّوبَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ نُهِيَ عَنْ رُكُوبِ الْجَلاَّلَةِ
also referenced under: Hadith 2557 (DarusSalam) & Hadith 2551 (Hasan)