Sahih Muslim Book 24, Hadith Number 5154.

Chapter : The use of gold and silver vessels to forbidden to men and women and it is also prohibited to drink in them.

Qatada reported: I heard Abe ‘Uthman al-Nahdi as saying: There came to us a letter of ‘Umar as we were in Adharba’ijan or in Syria in the company of ‘Utba b. Farqad (and the letter ran thus): After (usual praise and glorification of Allah) it is stated that Allah’s Messenger (may peace be upon him) has forbidden the use of silk but to the extent of these two fingers, and Abu Uthman said: We at once understood by these words that he meant (silk) patterns on (the cloth).