Ever since Arabic was spoken in the Arabian Peninsula, it borrowed words from persian. In the Pre-Islamic period, the most important Arabic document survived is the Jahiliyya period, on whose authenticity many scholars have cast doubts. In this collection of poems, there are about 100 words. In the Qur'an, too, which is the first written document in Arabic, there are about 30 Persian words. In the first century after Islam, the process of borrowing words from Persian was slow, but in the centuries that followed, the number of Persian loan words increased drastically. In Abu Novas' poems there are about 300 Persian words; in The Story of Abolqasem Bagdadi, written by Abu Motahhar Azdi, the number is 260, and in Tanuki's Nesvar, the number is 170. This paper limits itself to the book Nesvar. At first the writer refers to the knowledge about Iran and Iranians mentioned in the book. Then he explains twenty obsolete Persian words and finally presents the full list of Persian words used in the book.