Musnad Ahmad 1060:77

Muhammad ibn Ubayd narrated to us, al-A’mash narrated to us, from al-Musayyab ibn Rafi’, from Ali ibn Mudrik, who said: I saw Abu Ayyub take off his leather socks, so they looked at him. He said: "As for me, I have seen the Messenger of Allah, peace and blessings of Allah be upon him, wipe over them, but ablution has been made beloved to me."