Musannaf Ibn Abi Shayba 16:433

Abu Bakr narrated to us, he said: Muhammad ibn Abd Allah al-Asadi narrated to us, from Umar ibn Sa'id ibn Abi Husayn, from Ali ibn Abd Allah ibn Ali, he said: My father informed me that he heard Mu'awiyah while he was on the pulpit saying: The Messenger of Allah (may Allah bless him and grant him peace) forbade the wearing of silk and gold.