52:2At-Tur

‘A book was brought to Ibn Abbās which contained the verdicts of Alī, may Allah be pleased with him, and he effaced but a small amount,’ and Sufyān bin Uyaynah indicated with his arm .

When the Prophet (ﷺ) intended to write to the Byzantines, it was said to him, "Those people do not read your letter unless it is stamped." So the Prophet (ﷺ) took a silver ring and got 'Muhammad, the Apostle of Allah' engraved on it .... as if I am now looking at its glitter in his hand.

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.