High among the texts that have shaped Islamic culture and thought is al-Ghazālī’s masterpiece: “Iḥyā’ ‘Ulūm al-Dīn” (the Revival of Religious Sciences). Muslim scholars both in the east and west of the Islamic world have held different opinions as to whether it reached its goal of reviving the religious sciences. Many have rejected it on the grounds that it teaches numerous beliefs that contradict the teaching of Islam while others considered it to be the best presentation of Islamic spirituality and reflecting the essence of Islamic teaching. Muhammad b. Murtaḍa (1598–1680 C.E.), commonly called al-Fayd al-Kāshānī, was a prominent Shi‘a scholar who admired al-Ghazālī and acknowledged the originality of the “Iḥyā’” and its significant role in presenting Islamic ethics in a coherent manner. But at the same time he pointed to its shortcomings, claiming that it contained chapters alien to Islamic teaching and practices and that it relied on traditions (ahadith) that, according to his belief, are not reliable. Therefore, he undertook to edit (tahdhīb) the entire “Iḥyā’,” presenting a text that preserved the entire structure of the original work and most of al-Ghazālī’s theories but infusing it with Shi‘a traditions and beliefs. The full title of his work is “al-Mahajjah al-Bayḍā’ fi Tahdhīb al-Iḥyā’.” Since its publication this has become the standard textbook of Islamic ethics among Shi‘a scholars and communities. Moreover, al-Fayḍ mentioned that one of the reasons that led him to edit the “Iḥyā’” was his belief that al-Ghazālī later in his life converted to Shi’ism. In this paper I will analyze al-Kāshānī’s method of editing the “Iḥyā’” and examine his claim of al-Ghazālī’s conversion to Shi’ism. The importance of al-Kāshānī’s work is that it gives the reader a clear picture of the interaction between Shi’ism and Sunnism and highlights the main differences between them in terms of their beliefs and practices. It also provides us with insight into how Shi‘a scholars received Sufism.