Hisham bin Urwah (may Allah have mercy on him) narrates from his father that the ruling of the Qur'an returns to washing (i.e. the command is to wash the feet), and he recited "and (wash) your feet up to the ankles (wa arjulakum ila al-ka'bayn)" [Surah al-Ma'idah: 6] with the accusative (nasb).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 332