Abdullah bin al-Zubayr (may Allah be pleased with them both) said: Do not wear silk, for I heard Umar bin al-Khattab (may Allah be pleased with him) say that the Prophet (peace and blessings be upon him) said: "Whoever wears silk in this world will not wear it on the Day of Resurrection." Abdullah bin al-Zubayr (may Allah be pleased with them both) would say from himself that whoever does not wear silk clothing on the Day of Resurrection will not enter Paradise, because Allah's command is: "And their garments therein will be silk" [Surah al-Hajj: 23], and on that day the clothing of the people of Paradise will be silk.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4203