Musnad Ahmad 288:10

Bahz ibn Asad narrated to us, Hammad ibn Salamah narrated to us, Ya'la ibn 'Ata' informed us, from Aws ibn Abi Aws, who said: I saw my father one day perform ablution and wipe over his sandals. I said to him, "Do you wipe over them?" He replied, "This is how I saw the Messenger of Allah, peace and blessings of Allah be upon him, do."