Abu Dawud
Jihad
Book Number: 008 / Hadith Number: 2584
Narated By As-Sa'ib ibn Yazid : As-Sa'ib reported on the authority of a man whom he named: The Apostle of Allah (pbuh) put on two coats of mail during the battle of Uhud as a double protection. (The narrator is doubtful about the word zahara or labisa.)