Musnad Ahmad 524:7

Yunus narrated to us, Aban narrated to us, from Yahya—meaning Ibn Abi Kathir—who said: Abu Salamah ibn Abd al-Rahman narrated to me, from Ja'far ibn Amr ibn Umayyah, that his father narrated to him: "That he saw the Messenger of Allah, may Allah bless him and grant him peace, wiping over the khuffayn (leather socks)."