The Prophet ﷺ used to pray (the Nawafil) on his Mount facing east and whenever he wanted to offer the compulsory prayer, he used to dismount and face the Qibla.
أَنَّ النَّبِيَّ ﷺ كَانَ يُصَلِّي عَلَى رَاحِلَتِهِ نَحْوَ الْمَشْرِقِ فَإِذَا أَرَادَ أَنْ يُصَلِّيَ الْمَكْتُوبَةَ نَزَلَ فَاسْتَقْبَلَ الْقِبْلَةَ