Sunan an-Nasa'i, Volume 6, Book 48, Hadith 5279 (DarusSalam) ⓘ
It was narrated from Anas that : The Prophet [SAW] put on a silver ring with and Ethiopian stone (Fass), on which the inscription was: "Muhammad Rasul Allah."
أَخْبَرَنَا الْعَبَّاسُ بْنُ عَبْدِ الْعَظِيمِ، قَالَ حَدَّثَنَا عُثْمَانُ بْنُ عُمَرَ، قَالَ أَنْبَأَنَا يُونُسُ، عَنِ الزُّهْرِيِّ، عَنْ أَنَسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم اتَّخَذَ خَاتَمًا مِنْ وَرِقٍ وَفَصُّهُ حَبَشِيٌّ وَنَقْشُهُ مُحَمَّدٌ رَسُولُ اللَّهِ .
also referenced under: Hadith 5277 (Reference) & Book 48, Hadith 238 (In-Book)