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).
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ - وَاللَّفْظُ لاِبْنِ الْمُثَنَّى - قَالاَ حَدَّثَنَا مُحَمَّدُ، بْنُ جَعْفَرٍ حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، قَالَ سَمِعْتُ أَبَا عُثْمَانَ النَّهْدِيَّ، قَالَ جَاءَنَا كِتَابُ عُمَرَ وَنَحْنُ بِأَذْرَبِيجَانَ مَعَ عُتْبَةَ بْنِ فَرْقَدٍ أَوْ بِالشَّامِ أَمَّا بَعْدُ فَإِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنِ الْحَرِيرِ إِلاَّ هَكَذَا إِصْبَعَيْنِ . قَالَ أَبُو عُثْمَانَ فَمَا عَتَّمْنَا أَنَّهُ يَعْنِي الأَعْلاَمَ.
sunnah.com