The Prophet's Plans to spread the Message of Islam beyond Arabia

Late in the six year A.H., on his return from Hudaibiyah, the Prophet [pbuh] decided to send messages to the kings beyond Arabia calling them to Islam. In order to authenticate the credentials of his envoys, a silver seal was made in which were graven the words: "Muhammad the Messenger of All‚h" in the following formation: [Sahih Al-Bukhari 2/872,873]

[Picture not given right now - will be added later]

Envoys were chosen on the basis of their experience and knowledge, and sent on their errands in Muharram in the year 7 A.H., a few days before heading for Khaibar. [Rahmat-al-lil'alameen 1/171]