Anas b. Malik reported that when Messenger of Allah ﷺ decided to write letters to the Byzantine (Emperor) they (his Companions) told him that they would not read a letter unless it is sealed. (Then) Messenger of Allah ﷺ had a silver ring made (for himealf), (its shape is to vivid in my mind) as if I see its brightness in the band of Messenger of Allah ﷺ and its engravement was (Mubamrnad, Messenger of Allah).

حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ قَالَ ابْنُ الْمُثَنَّى حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، قَالَ سَمِعْتُ قَتَادَةَ، يُحَدِّثُ عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ لَمَّا أَرَادَ رَسُولُ اللَّهِ صلى اللهعليه وسلم أَنْ يَكْتُبَ إِلَى الرُّومِ - قَالَ - قَالُوا إِنَّهُمْ لاَ يَقْرَءُونَ كِتَابًا إِلاَّ مَخْتُومًا . قَالَفَاتَّخَذَ رَسُولُ اللَّهِ ﷺ خَاتَمًا مِنْ فِضَّةٍ كَأَنِّي أَنْظُرُ إِلَى بَيَاضِهِ فِي يَدِرَسُولِ اللَّهِ ﷺ نَقْشُهُ مُحَمَّدٌ رَسُولُ اللَّهِ .