It was narrated that Ibn 'Umar said: "The Prophet (ﷺ) used to wear a ring of gold, then he discarded it, and put on a ring of silver on which was engraved (the words): 'Muhammad Rasul Allah.' He said: 'No one else should engrave his ring with an inscription like this ring of mine.' Then he put the stone toward the palm of his hand."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ يَزِيدَ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ أَيُّوبَ بْنِ مُوسَى، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم تَخَتَّمَ خَاتَمًا مِنْ ذَهَبٍ ثُمَّ طَرَحَهُ وَلَبِسَ خَاتَمًا مِنْ وَرِقٍ وَنَقَشَ فِيهِ مُحَمَّدٌ رَسُولُ اللَّهِ وَقَالَ " لاَ يَنْبَغِي لأَحَدٍ أَنْ يَنْقُشَ عَلَى نَقْشِ خَاتَمِي هَذَا " . ثُمَّ جَعَلَ فَصَّهُ فِي بَطْنِ كَفِّهِ .
sunnah.com