The Sasanian state (227-635 AD) finally disintegrated at the hands of the armies of Islam. Extending their conquest beyond the Oxus river  they were to rule the country for many years. Years of war had enfeebled the country. Iran was unable to resist the Arab attacks with an exhausted army, a people in dire straits, an enfeebled religion, years of savagery and slaughter, the massacre and persecution of the Manichaeism and Mazdaism  at the instigation of the Zoroastrian priesthood, an increasingly gloomy and angry people, and a dearth of new thinking in their politics and beliefs.
Finally with two battles at Qadysiyya (635) and Nahavand (642) which the Arabs designated the victory of victories the Sasanian empire collapsed. Thereafter there was no governmental resistance against the Arabs. And in 652 with the fall of Gilan and Tabaristan  the last resistance of the people against the Arabs collapsed and they were in control of the entire country. But Iranian civilisation and culture, being more advanced than that of the conquerors, not only survived, but was passed on to the Arabs.
The official language of Iran during the Sasanian dynasty, and in the Zoroastrian religious establishment, was Pahlavi-Parsi. After the Arab conquest the Pahlavi language could not survive more than another three centuries. Yet "for some time in all the official writings [divan] of the Arab rulers in Iraq, Iran and the Transoxania the Pahlavi script and dialect was used" . The Pahlavi script, like many other practices and traditions could not ultimately compete against Arab culture. Because of the difficulty in reading and writing Pahlavi gradually gave way to the Arabic script, which was also the script for the Dari-Farsi language. It was only in the Zoroastrian temples that the Pahlavi script and language survived for a few more centuries.
The Arab conquest was followed by almost "two centuries of silence" over Iran. During this period nothing was seen from the new conquerors, bearers of a new culture and religion, but military and social violence. It took two centuries for the Iranians slowly, as a people with an independent identity, to come to themselves. Some accepted Islam, and seriously worked for it, translating remaining Pahlavi texts into Arabic and occupied important positions in the administrative and cultural system of the Arabs. Some of the same people tried to bring together Islam (the Qur'an) and ancient Iranian myths. Various histories relate that Zoroastra was the same as Abraham, or that Jamshid is another name for Solomon.
Arabic gradually replaced Pahlavi as the language of politics and religion. With decline of Pahlavi, other Iranian languages began to blossom. The Iranians did not bow to Islam easily. Such movements as Sho'ubieh, Shi'ism, mysticism and others, signify the cultural resistance. We also see military resistance and revolts right up to the fourth Islamic century such as the uprisings of Babak Khorramdin and Al-Moqanneh. It was through these encounters that the Iranians finally preserved their individual Iranian identity through, and under the cover, of the Farsi language. This was a great victory after the colossal defeat that had been inflicted on them.
With military resistance made impossible and with a foreign culture dominating the very being of the country, other ways were experimented with. Language became a sanctuary where the past history of Iran was celebrated so as to maintain national identity. The writing of many shahnameh (book of kings) came into vogue. And it was in these times that another group, the non-Muslims who had preferred paying tax and levy to accepting Islam , attempted to marshal their heritage. We find the efforts of the first group in such works as Khodainamak Garshaspnameh and ultimately in the Shahnameh (Book of Kings) by the epic poet Ferdowsi. The second group gathered and edited such works as Bandehash and Bahman Posht. In this way language and verse took on the most delicate role in expressing national feeling and Iranian identity. Language became a tool giving meaning to the very existence of Iranians. Farsi became the common sensibility of all Iranians.
The majority of historians of this era writing in Arabic were in fact Iranian. In compiling their histories, these people "in part modelled themselves on, and researched in, such books as the Pahlavi Khodainamak" . We could later see this influence in the works of Arab historians. For example such famous historians as Tabari and Yaqubi reproduced some of what was written in Khodainamak. Many modelled their style on Iranian works .
The more Islam took roots in Iran and spread, the more Arabic words entered the Iranian languages including the Farsi language and literature. Dari-Farsi came into more general use during the reign of Ya'qub Leith Saffari (dynasty began 867c), although it had already been the language of court and courtly letters. Its interaction with other local languages, as well as Arabic, allowed it to prosper, develop and spread. Poets began writing in this tongue. In a few decades Farsi literature - verse - found itself on par with Arabic poetry.
The history of Arabic literature prior to Islam was mostly oral and the Arabs on he whole saw no need to research or record their language. Pre-Islamic Arabic had little use for books though poetry had such a broad base that the best poems was hung on the walls of Ka'ba - the holiest shrine - a place of pilgrimage and worship. The pre-Islamic Arabs were electrified by poetry. They paid special heed to its pronunciation and diction. They paid even greater attention to the conjugation, syntax, vocabulary, and grammar of Arabic once Islam came to rule and relations with other languages widened.
The main themes of Arabic poetry were love, and physical pleasure which were described without any moralistic concerns or limitations. If the praise of war functioned to boost the combative spirit, women and wine were of the world of peace and of a life that could be pleasurable without any fear of the afterlife. The poet was held in high esteem and popularity. The poet was the pride of the tribe. Poetry was the most important pastime of the bedouin and a source of pride and honour. "The tribal poet had the task of spreading the glories of the tribe and supporting its designs. And because of the impact poetry had on these situations, the sheikh, the high born, the tribesmen and the people feared the poet's satire and were thrilled by his praise."
With the coming of Islam, the life Mohammad promised the believer was incompatible with the content of Arab poetry of the time. The Qur'an therefore presents poetry as worthless and absolves the prophet from it. A further consideration for Islam's hostility to poetry was beyond doubt the popularity of the poets. Poets held an exalted position in the tribe and their words could be decisive. The poet had the power to turn a conflict into peace or to incite tribal anger. Not unreasonably the Prophet saw them as rivals.
The poets saw that Islamic strictures inhibited their creation of poetry. In return Mohammad, in the name of God, called poets liars and Ali, Mohammad's son-in-law, refers to Amro al-Queiss, known as the "king of Arabic poets" as "king of the lost" . The Qur'an had little time for poets. From the beginning Islam was suspicious of them. The mystery and enigmas poetry has no place in the framework of Islamic laws. So we see that the Qur'an repudiates poetry and absolves the Prophet from being tainted by it. It calls on the learned men of its religion to distance themselves from it. Poetry is contemptible and the poet is a liar; "The Qur'an is in truth the revelation of God, and the utterance of a noble messenger. It is no poet's speech: scant is your faith! It is no soothsayer's divination: how little you reflect!" .
In the chapter Al-Shua'ra (the poets) the poet is equated with the unbeliever, the enemy of Islam: "poets (…) are followed by none save erring men. Behold how aimlessly they roam in every valley, preaching what they never practice. " . In the chapter Ya Sin the Qur'an emphasises the worthlessness of poetry "We have taught Mohammad no poetry, nor does it become to him to be a poet. This is but a warning: an eloquent Qur'an, to admonish the living and pass judgement on unbelievers" .
When the Prophet was told the Qur'an is like poetry he is reported to have become angry. There are many hadith (authenticated sayings) in which enmity with poetry is prominent. All the commentators of the Qur'an are insistent on this point. For example Abolfath Razi rejects the notion that the Qur'an is poetry and quotes Ayesheh, one of Mohammad's wives, that the prophet "has no greater enemy than poetry and it is in the news that the Prophet (peace be upon him and his offspring) if the stomach of one of you is filled with pus I would be happier than if were filled with poetry" .
Mohammad "reminded his followers of the pleasures that were being set aside for the saved" and promised them paradise "while his rival in Mecca, Nasr bin-Harath, recounted stories on such Iranian heroes as Rustam and Esfandyar and attracted the the Prophet's listeners to himself" . The Qur'an is the word of God, a revelation and its word is absolute. It is comprehensive and contains all the information and whatever is necessary for human life. "There is nothing, wet or dry, that has not appeared in the clear book [Qur'an]". Allah begins the chapter The Cow: "This Book is not to be doubted. [Q 2:1]
The Qur'an is a book on how to live. Its goal is the guidance of humankind. Whatever it bans is harmful for the "umma" (community of believers) and whatever it commands are for deliverance and well-being. The same chapter - The Cow - describes the grievous punishment unbelievers face.
And the poet is an unbeliever. The poverty of the bedouin Arab had made them into a materialist, one that is sceptical and pays little attention to life after death. The poet of the tribe is certainly someone who is sceptical. Eulogizing the dead after the battle of Badr, the poet laments "the Prophet promises us a resurrection, but how can such a new life come about?" 
Five hundred of the 6,000 verses in the Qur'an tell mankind what to do, known as the ahkam verses, or the Qur'anic jurisdiction (feqh al-Qur'an). The Qur'an is a collection of ethical and religious commandments which serve the function of the "constitution" of Islam. . Islam is built on the Qur'an. Allah in this book, in order to place Mohammad in a status above everyone else, a special being, absolves him from the accusation of being a poet. The Qur'anic chapter al-Anbiya' (The Prophets) addressed this: In private the unbelievers say to each other: 'is this man not a mortal like yourselves? …Some say: it [the Qur'an] is but a medley of dreams. Others: 'He has invented it himself' And yet others [say]: 'He is a poet: let him show us some sign, as did the apostles in days gone bye.' .
Whenever poetry appears in the Qur'an it is in a negative light. The chapter called The Pen (al-Qalam - Q 68) starts: 'By the pen, and what they [angels] write'. For years it was argued in Iran that it is to value and respect the pen that God swears by it. Yet a closer look at this chapter shows that God was talking of those who deny religion, belief and the Qur'an, and of the torments that await them. The pen in this chapter is the means whereby the angels record the deeds of the sinful umma for judgement day. This issue becomes more significant if we consider that the Arab at the inception of Islam was alien to the pen. Mohammad here uses the pen to strike fear into his umma, fear that is so essential to the survival of any religion.