that when Abu Bakr became the Caliph, he wrote a letter to him (and stamped it with the Prophet's ring) and the engraving of the ring was in three lines: Muhammad in one line, 'Apostle' in another line, and 'Allah' in a third line.  

أَنَّ أَبَا بَكْرٍ ؓ لَمَّا اسْتُخْلِفَ كَتَبَ لَهُ وَكَانَ نَقْشُ الْخَاتَمِ ثَلاَثَةَ أَسْطُرٍ مُحَمَّدٌ سَطْرٌ وَرَسُولُ سَطْرٌ وَاللَّهِ سَطْرٌ  

"The inscription on the ring of the Messenger of Allah [SAW] was: Muhammad Rasul Allah (Muhammad the Messenger of Allah).'"  

كَانَ نَقْشُ خَاتَمِ رَسُولِ اللَّهِ ﷺ مُحَمَّدٌ رَسُولُ اللَّهِ  

"The inscription on the ring of the Prophet ﷺ was in three lines: 'Muhammad' on a line, 'Messenger' on a line, and 'Allah' on a line." (Using translation from Tirmidhī 1747)   

«كَانَ نَقْشُ خَاتَمِ النَّبِيِّ ﷺ ثَلَاثَةَ أَسْطُرٍ مُحَمَّدٌ سَطْرٌ وَرَسُولُ سَطْرٌ وَاللَّهِ سَطْرٌ»  

"The inscription on the ring of the Prophet ﷺ was in three lines: 'Muhammad' on a line, 'Messenger' on a line, and 'Allah' on a line." (Using translation from Tirmidhī 1747)   

كَانَ «نَقْشُ خَاتَمِ النَّبِيِّ ﷺ ثَلَاثَةَ أَسْطُرٍ مُحَمَّدٌ سَطْرٌ وَرَسُولٌ سَطْرٌ وَاللَّهُ سَطْرٌ»  

"The inscription on the ring of the Prophet ﷺ was in three lines: 'Muhammad' on a line, 'Messenger' on a line, and 'Allah' on a line." (Using translation from Tirmidhī 1747)   

«كَانَ نَقْشُ خَاتَمِ النَّبِيِّ ﷺ ثَلَاثَةَ أَسْطُرٍ مُحَمَّدٌ سَطْرٌ وَرَسُولٌ سَطْرٌ وَاللَّهُ سَطْرٌ»  

"The inscription on the ring of the Messenger of Allah [SAW] was: Muhammad Rasul Allah (Muhammad the Messenger of Allah).'" (Using translation from Nasāʾī 5276)  

كَانَ نَقْشُ خَاتَمِ رَسُولِ اللهِ ﷺ مُحَمَّدٌ رَسُولُ اللهِ