(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
Abu 'Uthman reported:
While we were with 'Utba b. Farqad there came a letter of 'Umar (containing the instructions) that Allah's Messenger (ﷺ) had said: None should wear silk (with the exception of so much) but he will have nothing of it in the Hereafter. Abu 'Uthman said: To the extent of two fingers which are close to the thumb, and I was shown the (silk) borders of the Tayalisa mantle (which were about two fingers in breadth and I saw them.
Reference: Sahih Muslim 2069 e
In-book reference: Book 37, Hadith 28
USC-MSA web (English) reference(deprecated numbering scheme): Book 24, Hadith 5153