Sahih Bukhari Volume 003, Book 047, Hadith Number 788.
Narated By Ibn 'Umar : Umar saw a silken cloak over a man for sale and requested the Prophet to buy it in order to wear it on Fridays and while meeting delegates. The Prophet said, "This is worn by the one who will have no share in the Hereafter." Later on Allah's Apostle got some silken cloaks similar to that one, and he sent one to 'Umar. 'Umar said to the Prophet "How can I wear it, while you said about it what you said?" The Prophet said, "I have not given it to you to wear, but to sell or to give to someone else." So, 'Umar sent it to his brother at Mecca before he embraced Islam.