Sahih Bukhari
Dress
Volume: 007 / Book Number: 072 / Hadith Number: 720
Narrated Abu 'Uthman:
While we were with 'Utba. 'Umar wrote to us: The Prophet said, "There is none who wears silk in this world except that he will wear nothing of it in the Hereafter." ' Abu 'Uthman pointed out with his middle and index fingers.