Musnad Ahmad 987:9

Hassan ibn Musa and Husayn ibn Muhammad narrated to us, they said: Shayban narrated to us, from Yahya, from Abu Salamah, that Ja'far ibn 'Amr ibn Umayyah al-Damri informed him, that his father informed him that: "He saw the Prophet, peace and blessings of Allah be upon him, wiping over the khuffayn (leather socks)."