Abu Uthman says that we were with Sayyiduna Utbah bin Farqad (may Allah be pleased with him) when a letter from Sayyiduna Umar (may Allah be pleased with him) arrived, in which it was written: The Messenger of Allah (peace and blessings be upon him) said: "Whoever wears silk clothing in this world, except for such a small amount"—and the Prophet (peace and blessings be upon him) indicated with his finger—"he will have no share of silk in the Hereafter."
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 243