While we were with 'Utba b. Farqad there came a letter of 'Umar (containing the instructions) that Messenger of Allah 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. (Using translation from Muslim 2069e)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ «لَا يَلْبَسُ الْحَرِيرَ إِلَّا مَنْ لَيْسَ لَهُ مِنْهُ فِي الْآخِرَةِ شَيْءٌ إِلَّا هَكَذَا» وَقَالَ أَبُو عُثْمَانَ بِإِصْبَعَيْهِ اللَّتَيْنِ تَلِيَانِ الْإِبْهَامَ فَرَأَيْتُهُمَا أَزْرَارَ الطَّيَالِسَةَ حَتَّى رَأَيْتُ الطَّيَالِسَةَ