Jami` at-Tirmidhi, Volume 3, Book 22, Hadith 1748 (DarusSalam) ⓘ
Narrated Anas bin Malik: "The inscription on the ring of the Prophet was in three line: 'Muhammad' on a line, 'Messenger' on a line, 'Allah' on a line." And Muhammad bin Yahya (one of the two who narrated to him) did not say: "Three lines" in his narration. There are narrations on this topic from Ibn 'Umar. [Abu 'Eisa said:] This Hadith of Anas is a Hasan Sahih Gharib.
حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، وَمُحَمَّدُ بْنُ يَحْيَى، وَغَيْرُ، وَاحِدٍ، قَالُوا حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ الأَنْصَارِيُّ، حَدَّثَنِي أَبِي، عَنْ ثُمَامَةَ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ كَانَ نَقْشُ خَاتَمِ النَّبِيِّ صلى الله عليه وسلم ثَلاَثَةَ أَسْطُرٍ مُحَمَّدٌ سَطْرٌ وَرَسُولُ سَطْرٌ وَاللَّهِ سَطْرٌ . وَلَمْ يَذْكُرْ مُحَمَّدُ بْنُ يَحْيَى فِي حَدِيثِهِ ثَلاَثَةَ أَسْطُرٍ . وَفِي الْبَابِ عَنِ ابْنِ عُمَرَ .
also referenced under: Hadith 1748 (Reference) & Book 24, Hadith 29 (In-Book)