Yahya related to me from Malik from Abdullah ibn Dinar fromAbdullah ibn Umar that the Messenger of Allah, may Allah bless him andgrant him peace, used to pray on his mount while travelling, whicheverway it was facing. Abdullah ibn Dinar said, "Abdullah ibn Umar wouldalso do that."
USC-MSA web (English) reference: Book 9, Hadith 28
Arabic reference: Book 9, Hadith 357