(7) باب صَلاَةِ التَّطَوُّعِ عَلَى الدَّوَابِّ وَحَيْثُمَا تَوَجَّهَتْ بِهِ
Narrated Nafi`:
Ibn `Umar (while on a journey) used to offer the prayer and the witr on his mount (Rahila). He said that the Prophet (ﷺ) used to do so.
Reference: Sahih al-Bukhari 1095
In-book reference: Book 18, Hadith 15
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 20, Hadith 200