(2) باب تَحْرِيمِ اسْتِعْمَالِ إِنَاءِ الذَّهَبِ وَالْفِضَّةِ عَلَى الرِّجَالِ وَالنِّسَاءِ وَخَاتَمِ الذَّهَبِ وَالْحَرِيرِ عَلَى الرَّجُلِ وَإِبَاحَتِهِ لِلنِّسَاءِ وَإِبَاحَةِ الْعَلَمِ وَنَحْوِهِ لِلرَّجُلِ مَا لَمْ يَزِدْ عَلَى أَرْبَعِ أَصَابِعَ
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 (ﷺ) has forbidden the use of silk btit 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).
Reference: Sahih Muslim 2069 g
In-book reference: Book 37, Hadith 30
USC-MSA web (English) reference(deprecated numbering scheme): Book 24, Hadith 5154