Musnad Ahmad 435:103

'Abdullah ibn al-Harith narrated to us, he said: 'Umar ibn Sa'id ibn Abi Husayn narrated to me, that 'Ali ibn 'Abdullah ibn 'Ali al-'Adawi informed him, that his father informed him, he said: I heard Mu'awiyah on the pulpit in Makkah saying: "The Messenger of Allah, may Allah bless him and grant him peace, forbade the wearing of gold and silk."