Musannaf Ibn Abi Shayba 35:53

Yazid al-Taymi narrated to us, from Bakr, from Ibn al-Mughirah ibn Shu'bah, from his father, from the Prophet (may Allah bless him and grant him peace), that he wiped the front of his head and over the two leather socks (khuffayn), and he placed his hand upon the turban and wiped over the turban. And he mentioned that Abu Hanifah said: "Wiping over them (the turban and the socks) is not sufficient."