His Guidance in Da`wah to Rulers and Sending Them Envoys and Letters
When the Prophet returned from Hudaybiyyah, he wrote to kings around the world and sent his messengers to them. He addressed the Byzantine emperor by letter and through an emissary. He was inclined to Islam and on the verge of declaring it but he did not.
He sent a letter to an-Najashi (the ruler of Abyssinia), who embraced Islam.
He sent Abu Musa al-Ash`ari and Mu`adh bin Jabal to Yemen, where the general population embraced Islam willingly without battle.