That the Messenger of Allah ﷺ said: "Wearing silk and gold has made unlawful for the males of my Ummah and lawful for its females.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ حُرِّمَ لِبَاسُ الْحَرِيرِ وَالذَّهَبِ عَلَى ذُكُورِ أُمَّتِي وَأُحِلَّ لإِنَاثِهِمْ  

That 'Umar gave a Khutbah at Al-Jabiyah and he said: "The Messenger of Allah ﷺ prohibited silk except for two finger's worth of space, or three, or four."  

نَهَى نَبِيُّ اللَّهِ ﷺ عَنِ الْحَرِيرِ إِلاَّ مَوْضِعَ أُصْبُعَيْنِ أَوْ ثَلاَثٍ أَوْ أَرْبَعٍ