Musnad Ahmad 658:65

Abu Mu'awiyah narrated to us, Al-Shaybani narrated to us, from Ash'ath ibn Abi al-Sha'tha', from Mu'awiyah ibn Suwayd ibn Muqarrin, from Al-Bara' ibn 'Azib, who said: The Messenger of Allah, peace and blessings of Allah be upon him, commanded seven and forbade seven. He said: "He forbade wearing gold rings, drinking from silver vessels and gold vessels, wearing Dibaj (thin silk), silk, and Istabraq (thick silk), wearing Al-Qassi (a type of silk garment), and riding on red Maytharah (saddle cushions)." And he commanded seven: visiting the sick, following funeral processions, saying 'Yarhamuk Allah' (may Allah have mercy on you) to the one who sneezes, returning the greeting, fulfilling the oath of the one who swears, helping the oppressed, and answering the caller.