Musnad Ahmad 435:28

'Ali ibn Bahr narrated to us, he said: Al-Walid—meaning Ibn Muslim—narrated to us, he said: 'Abdullah ibn al-'Ala' narrated to us, that he heard Yazid—meaning Ibn Abi Malik—and Abu al-Azhar narrating about the ablution of Mu'awiyah. He said: "He was showing them the ablution of the Messenger of Allah, may Allah bless him and grant him peace." So he performed ablution three times [for each part], and he washed his feet without a [specific] count.