Abu Uthman reported,

We were with Utba bin Farqad when a letter from Umar came to us, stating that the Messenger of Allah ﷺ said, "No one wears silk except one who will have no share of it in the Hereafter, except this much." Abu Uthman indicated with his two fingers next to the thumb. Zirr said, I saw them as the buttons of the cloaks when I looked at the cloaks.

Muslim 5413

Sahih

و حدثنا ابن أبي شيبة وهو عثمان وإسحق بن إبراهيم الحنظلي كلاهما عن جرير واللفظ لإسحق أخبرنا جرير عن سليمان التيمي

عن أبي عثمان قال

كنا مع عتبة بن فرقد فجاءنا كتاب عمر أن رسول الله ﷺ قال لا يلبس الحرير إلا من ليس له منه شيء في الآخرة إلا هكذا وقال أبو عثمان بإصبعيه اللتين تليان الإبهام فرئيتهما أزرار الطيالسة حين رأيت الطيالسة

مسلم 5413صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Clothing and adornment
Chapter
Prohibition of using gold and silver vessels for men and women, gold rings and silk for men, their permissibility for women, and permissibility of silk borders and the like for men as long as it does not exceed four fingers
Numbering
Darussalam 5413
Muslim 5413