Yahya related to me from Malik from Nafi that Abdullah ibn Umarnever used to pray anything with the fard prayer, either before it orafter it, while travelling, except in the depths of the night. Hewould pray on the ground or on his mount, whichever way it was facing.
USC-MSA web (English) reference: Book 9, Hadith 24
Arabic reference: Book 9, Hadith 353