Mishkat al-Masabih

He said God’s messenger wore on his right hand a silver signet-ring with an Abyssinian stone, and put its stone next the palm of his hand. (Bukhari and Muslim.)

وَعَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَبِسَ خَاتَمَ فِضَّةٍ فِي يَمِينِهِ فِيهِ فَصٌّ حَبَشِيٌّ كَانَ يَجْعَلُ فَصَّهُ مِمَّا يَلِي كَفه