Sermon is one of traditional literary genres in Arabic and Persian literature. This literary genre was invented by Badio-zaman Hamedani (died in 398 of the Lunar year) employing the possibilities of Arabic language via addition and combining method and called it “Sermon”. Abolghasem Hariri (died in 516 L.) improved it into its perfect state in Arabic literature. In Arabic literature, sermon writing was not limited to prose works; through development and evolution it also appeared sometimes in poetry form. This genre was followed in Persian literature. Maintaining its principles and taking into account the requirements of Farsi language, Persian writers had some innovations in this rhetoric style. Sermons of Qazi Hamid-al-din Balkhi (died in 559 L.) are an example of sermon writing influenced by Arabic literature. In writing Golestan, which is in prose, Sa’adi, according to the conversant, followed the style of sermon writing. Moreover, by innovation and following Arab sermon writers who have turned to sermon writing in poetry due to fancy and innovation, he even prefers to try his aptitude in writing of sermons in Persian poetry. Perhaps hoping to create some literary innovations in this style, in case he succeeded in his approach and was accepted by the audience. At last, Saadi didn’t continue this method in poetry from. Due to his own preference or that of the audience of course, we know nothing about this matter. In this article we review a sample of poetic sermon, in Boustan.