Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
حَدَّثَنِي أَحْمَدُ بْنُ سَعِيدٍ أَبُو عَبْدِ اللَّهِ، حَدَّثَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، حَدَّثَنَا إِبْرَاهِيمُ بْنُ يُوسُفَ، عَنْ أَبِيهِ، عَنْ أَبِي إِسْحَاقَ، سَأَلَ رَجُلٌ الْبَرَاءَ وَأَنَا أَسْمَعُ، قَالَ أَشَهِدَ عَلِيٌّ بَدْرًا قَالَ بَارَزَ وَظَاهَرَ.Narrated Abu 'Is-haq:A man asked Al-Bara' and I was listening, "Did `Ali take part in (the battle of) Badr?" Al-Bara' said, "(Yes). he even met (his enemies) in a duel and was clad in two armors (one over the other)
From Sahih al-Bukhari, whose reports the scholars accept as authentic.