Musannaf Ibn Abi Shayba 1:1922

Abu Usama narrated to us, from al-A’mash, from Ibrahim al-Taymi, who said: I asked al-Harith ibn Suwayd about wiping over the leather socks (khuffayn). He said: "Wipe." I said: "Even if I enter the privy?" He said: "Even if you enter the privy ten times."