The advent of Islam brought a big transition in Arab society. Islam has influenced not only religious philosophy and behaviour patterns of people but also their social institutions and culture. However, the role of Islam has been negatively estimated by many scholars as the main sources of regression in the part of literature. It is mainly because arab poets` activities were declined and the number of collection of poems were decreased comparing to the era before and after the advent of Islam. Even, the poets were not revered as much as in the era before Islam. However, on the contrary to the general estimation of Islam and its negative influences on the Arabic literature, the article pays attention to the fact that Islam as a main source to develop the classical Arabic literature. For this, the article analyses classical Arabic language, poets and poems of that time as a mechanism of unification, and reveals the following conclusion. Firstly, Islam, as a source of unification, standardized and formalized classical Arabic language and popularized difficult Arabic poets. Second, Islam recognized poets as an artists and brought prosperity in Arabic literature. Lastly, Islam contributed in creating abundant Arabic expressions as many poets borrowed Quranic verses, the first Arabic book, in making phrases in their poems directly and indirectly.