From Sahih Bukhari (Hadith 3970):
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)
Reference: Bukhari 3970