The arrival of Islam in Iran

Islam is the official religion of Iran, and about 99 percent of the population is Muslim, and more than 90 percent of Muslims are Twelver Shiites. The process of converting Iranians to Islam began shortly after the Prophet Muhammad (peace be upon him) was sent as a prophet. The first group of Iranian Muslims at that time were Iranians from Yemen and Bahrain, and after that, following the Arab invasion of Iran, Iranians converted to Islam over the course of several centuries.
The equality and justice-oriented nature, simplicity and purity, tolerance and forgiveness, and the social and economic privileges of the Islamic religion caused this sacred law to take root in the hearts of the Iranian people in a short time.
The first group of Iranians to convert to Islam were a group of Iranians living in Yemen and Bahrain, which were considered part of the Iranian Empire during the Sasanian era.
At the time of the Prophet's (PBUH) call, the government of Yemen was in the hands of the Iranian (Bazan) ibn Sasan. Bazan ruled Yemen on behalf of Khosrow Parviz. When the Prophet invited Khosrow to Islam in the sixth year of the Hijri, he became very angry and tore up the Prophet's letter and wrote to Bazan (his agent in Yemen) to send the writer of the letter to him. Bazan sent two people to Medina to deliver Khosrow's message to the Prophet.
When the representatives were in the city of Medina, the Messenger of God, from the unseen, informed the Iranian representatives of the murder of Khosrow Parviz and the rise to power of his son Shirwayah, and told them: Your country will soon be conquered by the Muslims. You returned to Yemen and told Bazan to embrace Islam. When the truth of the matter became clear to Bazan, he embraced Islam, and then a group of Iranians, who were called "the sons of the freedmen," embraced Islam. These were the first Iranians to embrace the Islamic law. One of the most prominent reasons for the Sasanian powerlessness against the Muslims was the crisis of Iranian sovereignty in various fields; the tense situation and the crisis-ridden Sasanian society had made things easy for the Muslims. The absence of a central government, the disintegration of the Iranian army, especially after the defeat of Nahavand, the sabotage of some rulers, and the separatism of the peasants, greatly contributed to the superiority of the Muslims. Most of the cities of Iran were conquered by a peace treaty, and Muslims were obligated to support the People of the Book and preserve their ceremonies, temples, and Zoroastrian hearths.
Iranians felt the just system of Islam more when it was implemented by Imam Ali (AS), and according to some, this is also what caused them to gravitate towards the Prophet's family from the very beginning. Martyr Morteza Motahari believes: It was the interest, sincerity, and spirit of rightism that dominated Iranians that led to their approach to this religion and defense of its ideals in all periods of history and different geographical regions. The reason for this is the acceptance of the school of the Ahl al-Bayt (a.s.), who have shown an inclination and interest in it since the advent of Islam and who currently bear the burden of the mission of Shiism to the family of the Prophet (a.s.).
The prominent role of Iranians in the development of Islamic civilization and sciences, and the compilation of thousands of books in this field, is indicative of the deep love and interest of this people for the Islamic school. This love and devotion of Iranians has made this land the cradle of Islamic thinkers.

translator: fatemeh abbaszadeh