Musannaf Ibn Abi Shayba 35:58

Ibn ‘Ulayyah narrated to us, from Ayyub, from Nafi’, from Ibn ‘Umar, who said: A man said, "O Messenger of Allah, what should the *muhrim* (pilgrim in ihram) wear, or what should the *muhrim* leave?" He said: "He shall not wear the shirt, nor the trousers, nor the turban, nor the leather socks, unless he does not find sandals, then he may wear them below the ankles." And he mentioned that Abu Hanifah said: "He shall not do that; and if he does, then a blood sacrifice (*dam*) is upon him."