Imran bin Hittan asked Ibn Abbas (may Allah be pleased with them both) about silk, and he said: Ask Sayyidah Aishah (may Allah be pleased with her). I asked her, and she said: Ask Ibn Umar (may Allah be pleased with them both). I asked Ibn Umar (may Allah be pleased with them both), and he said: Abu Hafs (may Allah be pleased with him) narrated to me that the Messenger of Allah (peace and blessings be upon him) said: "Whoever wears silk in this world has no share in the Hereafter."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6064