Musnad Ahmad 30:1236

Abu al-Nadr narrated to us, al-Mubarak narrated to us, from al-Hasan, from Abu Hurayrah, who said: I heard the Prophet, peace and blessings of Allah be upon him, saying: "Indeed, the one who wears silk in this world is the one who does not hope to wear it in the Hereafter. Indeed, the one who wears silk is the one who has no share [in the Hereafter]." Al-Hasan said: "So what is the matter with people who receive this from their Prophet, yet they place silk in their garments and in their houses?"