The Messenger of Allah [SAW] granted a concession to 'Abdur-Rahman bin 'Awf and Az-Zubair bin Al-'Awwam allowing them to wear silken shirts because of scabies that they were suffering from.  

أَنَّ رَسُولَ اللَّهِ ﷺ أَرْخَصَ لِعَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ وَالزُّبَيْرِ بْنِ الْعَوَّامِ فِي قُمُصِ حَرِيرٍ مِنْ حِكَّةٍ كَانَتْ بِهِمَا  

The Prophet [SAW] granted a concession to 'Abdur-Rahman and Az-Zubair to wear silken shirts because of scabies that they were suffering from.  

أَنَّ النَّبِيَّ ﷺ رَخَّصَ لِعَبْدِ الرَّحْمَنِ وَالزُّبَيْرِ فِي قُمُصِ حَرِيرٍ كَانَتْ بِهِمَا يَعْنِي لِحِكَّةٍ  

"We were with 'Utbah bin Farqad when the letter of 'Umar came, saying that the Messenger of Allah [SAW] said: 'No one wears silk except one who has no share of it in the Hereafter, except this much.'" And Abu 'Uthman gestured with the two fingers that are next to the thumb. And I saw the two of them pointing to the borders of the Tayalisah, so that I could see the Tayalisah.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ يَلْبَسُ الْحَرِيرَ إِلاَّ مَنْ لَيْسَ لَهُ مِنْهُ شَىْءٌ فِي الآخِرَةِ إِلاَّ هَكَذَا وَقَالَ أَبُو عُثْمَانَ بِأُصْبُعَيْهِ اللَّتَيْنِ تَلِيَانِ الإِبْهَامَ فَرَأَيْتُهُمَا أَزْرَارَ الطَّيَالِسَةِ حَتَّى رَأَيْتُ الطَّيَالِسَةَ  

He did not allow the wearing of silk except (something) the width of four fingers.  

أَنَّهُ لَمْ يُرَخِّصْ فِي الدِّيبَاجِ إِلاَّ مَوْضِعَ أَرْبَعِ أَصَابِعَ