The Prophet (blessings and peace of Allah be upon him) used to write letters to the rulers of the earth at his time, calling them to enter Islam, in the hope that they would accept guidance and their people would be guided through them, without war. But they had some traditions with regard to correspondence. In this hadith, Anas ibn Malik (may Allah be pleased with him) narrates that our Prophet (blessings and peace of Allah be upon him) wanted to send a letter to one of the Persian rulers, or to the Byzantines, as it says in the report of al-Bukhari. But his companions told him that kings would not read any letters except those that had a seal bearing the signature of the sender. What is meant is a wax seal that was stamped with a name or a symbol that the sender had adopted for himself to seal and verify his letters. They would not read any letter unless it was sealed, for fear that their secrets might become known and their plans might be broadcast, and so as to be certain that the written contents had not been altered. So the Prophet (blessings and peace of Allah be upon him) acquired a ring of silver, because silver is not prohibited for men, and it may be worn on the hand, and he had it engraved with the second part of the shahadah: Muhammad Rasulullah (Muhammad [is] the Messenger of Allah). Then Anas (may Allah be pleased with him) stated that he used to look at the gleaming of the Prophet’s ring when it was worn on his hand. This hadith narrates how fresh this image of the ring and the Prophet’s wearing of it still was in his mind. From this hadith, we also learn that rulers, judges and governors may use seals on letters, and this is a tradition that is still practised. The hadith also indicates that it is prescribed to write to the disbelievers in ways that serve the interests of Islam and the Muslims. It also indicates that it is prescribed to engrave rings and to inscribe the name of the owner on the ring..