I saw the Prophet ﷺ offering the prayer on his mount (Rahila) whatever direction it took.  

رَأَيْتُ النَّبِيَّ ﷺ يُصَلِّي عَلَى رَاحِلَتِهِ حَيْثُ تَوَجَّهَتْ بِهِ  

The Prophet ﷺ used to offer the Nawafil, while riding, facing a direction other than that of the Qibla.  

أَخْبَرَهُ أَنَّ النَّبِيَّ ﷺ كَانَ يُصَلِّي التَّطَوُّعَ وَهْوَ رَاكِبٌ فِي غَيْرِ الْقِبْلَةِ  

Ibn ʿUmar (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.  

أَنَّ النَّبِيَّ ﷺ كَانَ يَفْعَلُهُ