‏الصلاة : Hadeeth No:1505 Salim b. 'Abdullah reported on the authority of his father that the Messenger of Allaah (sallAllaahu alayhi wa sallam) used to observe Nafl (supererogatory) prayer on his ride no matter in what direction it turned its face, and he observed Witr too on it, but did not observe obligatory prayer on it....

‏الجهاد والسير‏ : Hadeeth No:4407 The same tradition has been narrated through a different chain of transmitters on the authority of A'mash. This version contains the words: Ila amrin yofzi'una instead of Ila amrin na'rifuhu....