ENOfficial
Ibn 'Umar said: "The Prophet (Allah bless him and give him peace) chose a signet ring of silver, and put its stone in the part close to the palm of his hand. On it he engraved: “Muhammad is the Messenger of Allah,” and he forbade anyone to engrave on it. It is the one that fell from Mu'aiqib into the well of Aris.”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ أَبِي عُمَرَ، قَالَ: حَدَّثَنَا سُفْيان، عَنْ أَيُّوبَ بْنِ مُوسَى، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ: أَنَّ النَّبِيَّ صلى الله عليه وسلم اتَّخَذَ خَاتَمًا مِنْ فِضَّةٍ، وَجَعَلَ فَصَّهُ مِمَّا يَلِي كَفَّهُ، وَنَقَشَ فِيهِ مُحَمَّدٌ رَسُولُ اللهِ، وَنَهَى أَنْ يَنْقُشَ أَحَدٌ عَلَيْهِ وَهُوَ الَّذِي سَقَطَ مِنْ مُعَيْقِيبٍ فِي بِئْرِ أَرِيسٍ.
sunnah.com