Sahih al-Bukhari 4140
Sahih al-Bukhari · Book 64: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) · The Ghazwa of Anmar
Narrated Jabir bin `Abdullah Al-Ansari:
حَدَّثَنَا آدَمُ ، حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ ، حَدَّثَنَا عُثْمَانُ بْنُ عَبْدِ اللَّهِ بْنِ سُرَاقَةَ ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ الأَنْصَارِيِّ ، قَالَ رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم فِي غَزْوَةِ أَنْمَارٍ يُصَلِّي عَلَى رَاحِلَتِهِ، مُتَوَجِّهًا قِبَلَ الْمَشْرِقِ مُتَطَوِّعًا .
I saw the Prophet (ﷺ) offering his Nawafil prayer on his Mount facing the East during the Ghazwa of Anmar.