Musnad Ahmad 435:108

Khalaf ibn al-Walid narrated to us, he said: Ibn ‘Ayyash—meaning Isma‘il—narrated to us, from ‘Abdullah ibn Dinar and others, from Abu Hurayz, the freed slave of Mu‘awiyah, who said: Mu‘awiyah delivered a sermon to the people in Homs, and he mentioned in his sermon: That the Messenger of Allah (may Allah bless him and grant him peace) prohibited seven things, and I am informing you of that and forbidding you from it. Among them are: wailing, poetry, images, the display of adornment (tabarruj), the skins of predatory animals, gold, and silk.