Sunan Abi Dawud, Hadith 4220

The tradition mentioned above has also been transmitted by Ibn 'Umar through different chain of narrators from the Prophet. This version adds: They searched for it but could not find it. 'Uthman then fashioned a signet-ring and engraved on it "Muhammad, the Messenger of Allah". He used to wear it or stamp with it.

حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى بْنِ فَارِسٍ، حَدَّثَنَا أَبُو عَاصِمٍ، عَنِ الْمُغِيرَةِ بْنِ زِيَادٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، بِهَذَا الْخَبَرِ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ فَالْتَمَسُوهُ فَلَمْ يَجِدُوهُ فَاتَّخَذَ عُثْمَانُ خَاتَمًا وَنَقَشَ فِيهِ ‏ "‏ مُحَمَّدٌ رَسُولُ اللَّهِ ‏" ‏ ‏.‏ قَالَ فَكَانَ يَخْتِمُ بِهِ أَوْ يَتَخَتَّمُ بِهِ ‏.‏

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also referenced under: Hadith 4208 (Hasan)