This hadith has been reported on the authority of Qatada but there is no mention of the words of Abd Uthman.
Sahih Muslim Book 37, Hadith 31
← Previous Hadith 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).

Sahih Muslim Book 37, Hadith 30 Next Hadith → 'Umar addressed us at a place known as Jabiya (Syria) and he said: Allah's Apostle (ﷺ) forbade us the wearing of silk but to the extent of two or three fingers or four fingers.

Sahih Muslim Book 37, Hadith 32