Musnad Abu Ya'la al-Mawsili 151:17

Ahmad ibn Hatim narrated to us, [he said] Khalaf—meaning ibn Khalifah—narrated to us, from Humayd—meaning al-A'raj—from Abdullah ibn al-Harith, from Ibn Mas'ud, from the Prophet (peace be upon him), who said: "Allah spoke to Musa while he was wearing a jubbah (outer garment) of wool, a cloak of wool, trousers of wool, and a cap of wool, and his sandals were of the hide of an unslaughtered donkey."