Musnad Ahmad 25:1603

'Abd al-Razzaq narrated to us, Ibn Jurayj and Rawh informed us, they said: Ibn Jurayj narrated to us, he said: Khasif informed me that Miqsam, the freed slave of 'Abd Allah ibn al-Harith ibn Nawfal, informed him that Ibn 'Abbas informed him, he said: I was with 'Umar when Sa'd and Ibn 'Umar asked him about wiping over the leather socks (khuffayn). 'Umar gave a ruling in favor of Sa'd. Ibn 'Abbas said: So I said, "O Sa'd, we know that the Prophet, peace and blessings of Allah be upon him, wiped over his leather socks, but was it before the [revelation of the] Table (al-Ma'idah), or after it?" Rawh said: "Or after it?" He said: "No one can tell you that the Prophet, peace and blessings of Allah be upon him, wiped over them after the Table was revealed." So 'Umar remained silent.