Saadi, a prominent Iranian poet, with the creation of two books, Bostan and Golestan, as masterpieces of didactic literature, represents and testifies to the rich and fruitful Iranian culture. The topic of man and God and related issues are comprehensively present in Bostan and Golestan in a unique way. He has been able to combine poetry, music, and speech with wisdom and advice. Given the influence of religious teachings and Islamic culture on Saadi's thought, as well as its impact on the writing of Bostan and Golestan, and the many similarities between the two with religious works, especially Nahj al-Balaghah, this article examines the relationship between man and God in the books Bostan and Golestan as representatives of didactic literature and compares it with Letter 31 of Nahj al-Balaghah as an educational and religious charter. This writing is descriptive and analytical, and library resources were used for its preparation and compilation. The results of this comparison show that in both works, the pivotal relationship of man with God is emphasized based on knowledge and understanding, gratitude, prayer and repentance, submission and contentment, piety and servitude, and this aspect is one of the many similarities between the two works; to the extent that at times Saadi has been able to express the essence of the relationship between man and God with the least difference in understanding and even in parallel with Letter 31 of Nahj al-Balaghah.