I saw the Prophet ﷺ offering his Nawafil prayer on his Mount facing the East during the Ghazwa of Anmar.  

رَأَيْتُ النَّبِيَّ ﷺ فِي غَزْوَةِ أَنْمَارٍ يُصَلِّي عَلَى رَاحِلَتِهِ مُتَوَجِّهًا قِبَلَ الْمَشْرِقِ مُتَطَوِّعًا