Musnad Ahmad 27:408

Yazid narrated to us, Jarir ibn Hazim informed us, Nafi’ narrated to us, he said: Ibn Umar found the cold while he was in the state of Ihram, so he said: "Cast a garment upon me." So I cast a burnous (hooded cloak) upon him. He pushed it away and said: "You cast upon me a garment that the Messenger of Allah, may Allah bless him and grant him peace, has forbidden the one in Ihram to wear."