Ash-Shama'il Al-Muhammadiyah, Book 46, Hadith 315 (English)

Anas Radiyallahu 'Anhu reports: "Rasulullah Sallallahu 'Alayhi Wasallam visited the sick, attended funerals, rode on donkeys, accepted the invitations of slaves. On the day of the battle of Banu Qurayzah, he rode on a donkey, the reigns of which were made of date palm leaves. On it was also a saddle made of date palm leaves".

حَدَّثَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ‏:‏ حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنْ مُسْلِمٍ الأَعْوَرِ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ‏:‏ كَانَ رَسُولُ اللهِ صلى الله عليه وسلم يَعُودُ الْمَرِيضَ، وَيَشْهَدُ الْجَنَائِزَ، وَيَرْكَبُ الْحِمَارَ، وَيُجِيبُ دَعْوَةَ الْعَبْدِ، وَكَانَ يَوْمَ بَنِي قُرَيْظَةَ عَلَى حِمَارٍ مَخْطُومٍ بَحَبْلٍ مِنْ لِيفٍ، وَعَلَيْهِ إِكَافٌ مِنْ لِيفٍ‏.‏

also referenced under: Book 47, Hadith 332 (In-Book)