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Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
nasai-kubra:9554 – Maḥmūd b. Ghaylān > al-Faḍl / Ibn Mūsá > Ismāʿīl > ʿĀmir > Sūwayd b. Ghafalah

[Machine] Umar said, "Wear silk like this and this, with two fingers or three or four."  

الكبرى للنسائي:٩٥٥٤ – أَخْبَرَنَا مَحْمُودُ بْنُ غَيْلَانَ قَالَ أَخْبَرَنَا الْفَضْلُ يَعْنِي ابْنَ مُوسَى عَنْ إِسْمَاعِيلَ عَنْ عَامِرٍ عَنْ سُوَيْدِ بْنِ غَفَلَةَ قَالَ

قَالَ عُمَرُ «الْبَسُوا مِنَ الْحَرِيرِ هَكَذَا وَهَكَذَا إِصْبَعَيْنِ أَوْ ثَلَاثَةً أَوْ أَرْبَعَةً»  

See similar narrations below:

Collected by Abū Dāwūd
abudawud:4042 – Mūsá b. Ismāʿīl > Ḥammād > ʿĀṣim al-Aḥwal > Abū ʿUthmān al-Nahdī > Katab ʿUmar > ʿUtbah b. Farqad

'Umar wrote to 'Utbah b. Farqad that the Prophet ﷺ forbade (wearing) silk except so-and-so, and so-and-so, to the extent of two, three, or four fingers.  

أبو داود:٤٠٤٢ – حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ حَدَّثَنَا حَمَّادٌ حَدَّثَنَا عَاصِمٌ الأَحْوَلُ عَنْ أَبِي عُثْمَانَ النَّهْدِيِّ قَالَ كَتَبَ عُمَرُ إِلَى عُتْبَةَ بْنِ فَرْقَدٍ

أَنَّ النَّبِيَّ ﷺ نَهَى عَنِ الْحَرِيرِ إِلاَّ مَا كَانَ هَكَذَا وَهَكَذَا أُصْبُعَيْنِ وَثَلاَثَةً وَأَرْبَعَةً