The Qur'anic verses 18:60-82 in Sūrat al-Kahf present the story of Khiḍr and Moses as a lesson on the modalities of being and of knowing. Traditionally, the story is seen from a variety of vantage points that include historical, textual, literary, and allegorical, each of which is framed differently depending on the religio-cultural context. This book, in addition to examining the theological sources, traces the story's mythical, mystical, and popular interpretations engendered by the Qur'anic story. The author argues that the story's major contribution is its ability to communicate the importance of cultivating humility--a fundamental goal for any person of faith. Despite his importance in the Qur'an, Moses is not the main hero in this story; instead, he is used to point to an even higher truth pertaining to the spiritual dimensions of faith. This book suggests that Khiḍr's Qur'anic story symbolizes these truths by providing a perspective on the tension between materiality and spirituality, the ẓāhir (exoteric) and the bāṭin (esoteric), and human and divine forms of knowledge. Additionally, in this work, the Khiḍr narrative is viewed as a source of nourishment for theories that speak to the intersectionality between Islam and other religious traditions.