Musannaf Ibn Abi Shayba 16:574

Abu Bakr narrated to us, he said: Ishaq bin Mansur narrated to us, he said: Al-Rabi’ bin Al-Mundhir narrated to us, from his father, that he saw upon Muhammad bin Al-Hanafiyyah a *hibra* (garment) with the buttons removed. And he had a *burnus* (hooded cloak) made of silk.