Sahih Bukhari Volume 8, Book 73, Hadith Number 104.

Narated By ‘Abdullah : ‘Umar saw a silken cloak over a man (for sale) so he took it to the Prophet and said, ‘O Allah’s Apostle! Buy this and wear it when the delegate come to you.’ He said, ‘The silk is worn by one who will have no share (in the Here-after).’ Some time passed after this event, and then the Prophet sent a (similar) cloak to him. ‘Umar brought that cloak back to the Prophet and said, ‘You have sent this to me, and you said about a similar one what you said?’ The Prophet said, ‘I have sent it to you so that you may get money by selling it.’ Because of this, Ibn ‘Umar used to hate the silken markings on the garments.