Riyad-us-Saliheen 805
'Umar bin Al-Khattab (May Allah be pleased with him) reported: I heard Messenger of Allah (PBUH) saying, "Silk (clothes) are worn only by him who has no share in the Hereafter."
[Al-Bukhari and Muslim]
This Hadith tells us that men will fall into a serious error if they wear dress made from silk. And if they do not sincerely repent for it, they will undoubtedly be punished in Hell-fire.