Musannaf Ibn Abi Shayba 1:1860

Abu Mu'awiyah narrated to us, from al-A'mash, from al-Hakam, from 'Abd al-Rahman ibn Abi Layla, from Ka'b ibn 'Ujrah, from Bilal, that the Messenger of Allah (may Allah bless him and grant him peace) wiped over the khuffayn (leather socks) and the khimar (head covering).