While we were at Adharbijan, `Umar wrote to us: 'Allah's Messenger (ﷺ) forbade wearing silk except this much. Then the Prophet (ﷺ) approximated his two fingers (index and middle fingers) (to illustrate that) to us.' Zuhair (the sub-narrator) raised up his middle and index fingers.
Sahih al-Bukhari Book 77, Hadith 46
← Previous Hadith While we were with `Utba bin Farqad at Adharbijan, there came `Umar's letter indicating that Allah's Apostle had forbidden the use of silk except this much, then he pointed with his index and middle fingers. To our knowledge, by that he meant embroidery.

Sahih al-Bukhari Book 77, Hadith 45 Next Hadith → While we were with `Utba. `Umar wrote to us: The Prophet (ﷺ) said, "There is none who wears silk in this world except that he will wear nothing of it in the Hereafter." ' Abu `Uthman pointed out with his middle and index fingers.

This hadith has also been narrated by Abu `Uthman.

Sahih al-Bukhari Book 77, Hadith 47