Musannaf Ibn Abi Shayba 16:558

Abu Bakr narrated to us, he said: Abd al-Rahim narrated to us, from Ubayd Allah, from Nafi, from Sa'id ibn Abi Nadra, from Abu Musa, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Silk and gold are forbidden for the males of my nation, and lawful for their females."