Mishkat al-Masabih 4383
Ibn ‘Umar said the Prophet took a signet-ring of gold. A version:
says he put it on his right hand, then threw it away and took one of silver on which he engraved, “Muhammad God’s messenger,” saying, “No one must engrave anything in the manner of this signet-ring of mine.” When he wore it he put the stone next the palm of his hand. 
(Bukhari and Muslim.)
عَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا قَالَ: اتَّخَذَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ خَاتَمًا مِنْ ذَهَبٍ وَفِي رِوَايَةٍ: وَجَعَلَهُ فِي يَدِهِ الْيُمْنَى ثُمَّ أَلْقَاهُ ثُمَّ اتَّخَذَ خَاتَمًا مِنْ الْوَرق نُقِشَ فِيهِ: مُحَمَّدٌ رَسُولُ اللَّهِ وَقَالَ: «لَا يَنْقُشَنَّ أَحَدٌ عَلَى نَقْشِ خَاتَمِي هَذَا» . وَكَانَ إِذَا لَبِسَهُ جَعَلَ فَصَّهُ مِمَّا يَلِي بَطْنَ كَفه