Abu Uthman reported,

We were with Utba bin Farqad when Umar wrote to him conveying things he was reporting from the Prophet ﷺ. Among what he wrote was that the Messenger of Allah ﷺ said, "No one wears silk in this world except that he will have no share of it in the Hereafter, except for this much," and he indicated with his two fingers, the index and the middle finger.Abu Uthman said, "I understood this to refer to the buttons on cloaks, when we later saw such cloaks."

حدثنا يحيى بن سعيد حدثنا التيمي

عن أبي عثمان رضي الله عنه قال

كنا مع عتبة بن فرقد فكتب إليه عمر رضي الله عنه بأشياء يحدثه عن النبي ﷺ فكان فيما كتب إليه أن رسول الله ﷺ قال لا يلبس الحرير في الدنيا إلا من ليس له في الآخرة منه شيء إلا هكذا وقال بإصبعيه السبابة والوسطى قال أبو عثمان فرأيت أنها أزرار الطيالسة حين رأينا الطيالسة