The Holy Prophet's Letters and the spread of Islam

The letters written by the Prophet (peace be upon him) to the kings and heads of different tribes was part of his prophethood for call unto Islam which announced the divine message to the people of thatera and made the Divine Order prevail. Although all the recipients had not positively replied, it prepared the way for their familiarity with Islam, and since one of the important missions of all prophets is announcement and conveying message, they fulfilled their duties at the first stage and on the other part it was an ultimatum to those who received the prophet's letters. Attention to the content of these lettersshow that the prophet's procedure was based on wisdom, awakeing and peace and he refrained from any threat, violence, fear and intimation. This issue is considered as one of the philosophical methods for spreading Islam at the prophet's era.