Abu Uthman Nahdi reported,

Umar wrote to us while we were in Adharbayjan, "Utba bin Farqad, this wealth is not from your own toil, nor from the toil of your father, nor from the toil of your mother. So give the Muslims their fill in their camps of what you have your fill of in your own camp. Beware of luxury, and of the dress of the people of shirk, and of wearing silk, for the Messenger of Allah ﷺ forbade the wearing of silk."He said, "Except for this much," and the Messenger of Allah ﷺ raised for us his two fingers, the middle finger and the index finger, and put them together.Zuhayr said that Asim said this part is in the letter. And Zuhayr raised his own two fingers.

Muslim 5412

Sahih

حدثني زهير بن حرب حدثنا جرير بن عبد الحميد ح و حدثنا ابن نمير حدثنا حفص بن غياث كلاهما عن عاصم بهذا الإسناد عن النبي ﷺ في الحرير بمثله

مسلم 5412صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Clothing and adornment
Chapter
Prohibition of using gold and silver vessels for men and women, gold rings and silk for men, their permissibility for women, and permissibility of silk borders and the like for men as long as it does not exceed four fingers
Numbering
Darussalam 5412
Muslim 5412