Finally these two customs and traditions merged and a "Iranian Islamic" identity as a new identity has emerged.
The Islamization of Iran was to yield deep transformations within the cultural, scientific, and political structure of Iran's society: The blossoming of Persian literature, philosophy, medicine and art became major elements of the newly-forming Muslim civilization. Inheriting a heritage of thousands of years of civilization, and being at the "crossroads of the major cultural highways", contributed to Persia emerging as what culminated into the "Islamic Golden Age". During this period, hundreds of scholars and scientists vastly contributed to technology, science and medicine, later influencing the rise of European science during the Renaissance.
It is difficult to imagine the Arabs especially Ummayad dynasty not implementing anti-Persian policies in light of such events, writes Zarrinkoub in his famous Two centuries of silence, where he exclusively writes of this topic . Reports of Persian speakers being tortured are also given in Abū al-Faraj al-Isfahāni's al-Aghānī.
However after the reign of the Umayyads, Iran and its society in particular experienced reigning dynasties who legitimize Persian languages and customs.
There are a number of historians who see the rule of the Umayyads as setting up the "dhimmah" to increase taxes from the dhimmis to benefit the Arab Muslim community financially and by discouraging conversion. Islam was initially associated with the ethnic identity of the Arab and required formal association with an Arab tribe and the adoption of the client status of mawali. Governors lodged complaints with the caliph when he enacted laws that made conversion easier, depriving the provinces of revenues.Abbassid period an enfranchisement was experienced by the mawali and a shift was made in political conception from that of a primarily Arab empire to one of a Muslim empire and c. 930 a requirement was enacted that required all bureaucrats of the empire be Muslim. Both periods were also marked by significant migrations of Arab tribes outwards from the Arabian Peninsula into the new territories.
Richard Bulliet's "conversion curve" and relatively minor rate of conversion of non-Arab subjects during the Arab centric Umayyad period of 10%, in contrast with estimates for the more politically multicultural Abassid period which saw the Muslim population go from approx. 40% in the mid 9th century to close to 80% by the end of 11th century.
The emergence of Iranian Muslim dynasties has great effect on changing religion as Seyyed Hossein Nasr says. These dynasties have adopted some Persian language cultural values and adapted them with Islam.
In the 9th and 10th centuries, non-Arab subjects of the Ummah created a movement called Shu'ubiyyah in response to the privileged status of Arabs. Most of those behind the movement were Persian, but references to Egyptians, Berbers and Aramaeans are attested. Citing as its basis Islamic notions of equality of races and nations, the movement was primarily concerned with preserving Persian culture and protecting Persian identity, though within a Muslim context. The most notable effect of the movement was the survival of the Persian language to the present day. It's a response to the growing Arabization of Islam in the earlier centuries. It was primarily concerned with preserving Persian culture and protecting Persian identity. The most notable effect of the movement was the survival of Persian language, the language of the Persians, to the present day. The movement never moved into apostasy though, and has its basis in the Islamic thought of equality of races and nations.
The Abbasids also held a strong pro-Iranian campaign against the Ummayads in order to get support from the Persian population. After their establishment as Caliphs, holidays such as Nowruz for example were permitted after a long suppression by the Ummayad rulers. The Abbasids, in particular al-Mamun, also actively promoted the Persian language. On the other hand, many of initial Muslim rulers of Iranian origin did not have an interest in the Persian language. Neither the Tahirids nor the Saffarids, who were of Persian stock, favoured the use of Persian instead of Arabic at their courts at Nishapur and Sistan, and even the last member of the Tahirid dynasty was noted for his fine Arabic style. The Tahirid dynasty, who were nominally subject to the Abbasid caliphs, had a very strict Islamist view which sometimes lead to anti-Zoroastrian policies.
The Samanid dynasty was the first fully native dynasty to rule Iran since the Muslim conquest, and led the revival of Persian culture. The first important Persian poet after the arrival of Islam, Rudaki, was born during this era and was praised by Samanid kings. The Samanids also revived many ancient Persian festivals. Their successor, the Ghaznawids, who were of non-Iranian Turkic origin, also became instrumental in the revival of Persian.
The Shi'a Buwayhid rulers, adopted a similar attitude in this regard. They tried to revive many of the Sassanid customs and traditions. They even adopted the ancient Persian title of Shahanshah (King of Kings) for their rulers.
According to Bernard Lewis:
"Iran was indeed Islamized, but it was not Arabized. Persians remained Persians. And after an interval of silence, Iran reemerged as a separate, different and distinctive element within Islam, eventually adding a new element even to Islam itself. Culturally, politically, and most remarkable of all even religiously, the Iranian contribution to this new Islamic civilization is of immense importance. The work of Iranians can be seen in every field of cultural endeavor, including Arabic poetry, to which poets of Iranian origin composing their poems in Arabic made a very significant contribution. In a sense, Iranian Islam is a second advent of Islam itself, a new Islam sometimes referred to as Islam-i Ajam. It was this Persian Islam, rather than the original Arab Islam, that was brought to new areas and new peoples: to the Turks, first in Central Asia and then in the Middle East in the country which came to be called Turkey, and of course to India. The Ottoman Turks brought a form of Iranian civilization to the walls of Vienna..."
Persians had a great influence on their conquerors. The caliphs adopted many Sassanid administrative practices, such as coinage, the office of vizier, or minister, and the divan, a bureaucracy for collecting taxes and giving state stipends. Indeed, Persians themselves largely became the administrators. It is well established that the Abbasid caliphs modeled their administration on that of the Sassanids. The caliphs adopted Sassanid court dress and ceremony. In terms of architecture Islamic architecture borrowed heavily from Persian architecture. The Sassanid architecture had a distinctive influence over Islamic architecture.
Iranians, since the beginning had interest and sincere efforts in compiling the study of Arabic etymology, grammar, syntax, morphology, figures of speech, rules of eloquence, rhetoric. Arabic was not seen as an alien language but the language of Islam and thereby Arabic was widely accepted as an academic and religious language and embraced in many parts of Iran. It was for the sake of the Qur'an and Islam that books of philosophy, mysticism, history, medicine, mathematics and law had been written or translated into this language.
The New Persian language after Islam, unlike Pahlavi, introduced a decent amount of Arabic vocabulary, which made New Persian a popular language with a famous literature which its predecessor had not been. The newly introduced Arabic words made New Persian more complete which fortified the Islamic golden age as well as Persian literature and poetry in the late middle ages. New Persian represented a new tradition formed by Muslim Persians well versed in Arabic, but with a love for their own spoken language. The New Persian language written in the Arabic alphabet with a some modifications was formed in the ninth century in eastern Iran and came to flourish in Bukhara, the capital of the Persian Samanid dynasty.
Persian language, because of its strong support from Abassid rulers condoning the language became one of the universal Islamic language, next to Arabic.
The most important scholars of almost all of the Islamic sects and schools of thought were Persian or live in Iran including most notable and reliable Hadith collectors of Shia and Sunni like Shaikh Saduq, Shaikh Kulainy, Imam Bukhari, Imam Muslim and Hakim al-Nishaburi, the greatest theologians of Shia and Sunni like Shaykh Tusi, Imam Ghazali, Imam Fakhr al-Razi and Al-Zamakhshari, the greatest physicians, astronomers, logicians, mathematicians, metaphysicians, philosophers and scientists like Al-Farabi, Avicenna, and Nasīr al-Dīn al-Tūsī, the greatest Shaykh of Sufism like Rumi, Abdul-Qadir Gilani.
Ibn Khaldun narrates in his Muqaddimah :
It is a remarkable fact that, with few exceptions, most Muslim scholars…in the intellectual sciences have been non-Arabs, thus the founders of grammar were Sibawaih and after him, al-Farsi and Az-Zajjaj. All of them were of Persian descent they invented rules of (Arabic) grammar. Great jurists were Persians. Only the Persians engaged in the task of preserving knowledge and writing systematic scholarly works. Thus the truth of the statement of the prophet (Muhammad) becomes apparent, 'If learning were suspended in the highest parts of heaven the Persians would attain it"…The intellectual sciences were also the preserve of the Persians, left alone by the Arabs, who did not cultivate them…as was the case with all crafts…This situation continued in the cities as long as the Persians and Persian countries, Iraq, Khorasan and Transoxiana (modern Central Asia), retained their sedentary culture.
One Abbasid caliph is even quoted as saying:
Despite the message of equality embedded in the new religion of Islam, the Arab conquerors, according to many historians, formed "a ruling aristocracy with special rights and privileges, which they emphatically did not propose to share with the mawali". Some rulers, such as Hajjaj ibn Yusuf even went as far as viewing the Mawali as "barbarians", implementing harsh policies such as branding to keep the subjects in check.
The case of Hajjaj is particularly noteworthy as many reports have come down to us from his racial policies and iron tactics in governing the provinces. And yet many skeptics point to the fact that some of these reports were written by Abbasid era writers who may have had a skewed view of their predecessors.
However Hajjaj was not the only case of cruelty against the Mawali. The non-Iranian appointee of the Caliph in Isfahan for example cut off the heads of any of the Mawali who failed to pay their taxes, and Ibn Athir in his al-kāmil reports that Sa'id ibn al'Ās killed all but one person in the port city of Tamisah, during his incursion to Gorgan in the year 651CE.