Mishkat al-Masabih 29 Excellent Qualities and Description of the Prophet كتاب الفضائل والشمائل 133

وَعَنْ سَعْدِ بْنِ أَبِي وَقَّاصٍ قَالَ: رَأَيْتُ عَنْ يَمِينُ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَعَنْ شِمَالِهِ يَوْمَ أُحُدٍ رَجُلَيْنِ عَلَيْهِمَا ثِيَابٌ بِيضٌ يُقَاتِلَانِ كَأَشَدِّ الْقِتَالِ مَا رأيتُهما قبلُ وَلَا بعد يَعْنِي جِبْرِيل وَمِيكَائِيل. مُتَّفق عَلَيْهِ

Sa`d b. Abu Waqqas told that at the battle of Uhud he saw two men in white clothing whom he had never seen before or since fighting as violently as possible on the right and left of God’s messenger, meaning Gabriel and Michael. (Bukhari and Muslim.)