Musnad Ahmad 1167:82

Narrated to us Nasr ibn Bab, from Hajjaj, from Abu Umar, a son-in-law who was to Ata: Asma brought out for us a jubbah (outer garment) with a border of silk. She said: "The Messenger of Allah, peace and blessings of Allah be upon him, used to wear this when he encountered war."