"Kitab Ar Ruh" (The Book of the Soul) is a renowned book written by the eminent Islamic scholar, Ibn Qayyim al-Jawziyah (1292-1350 CE). The book is a comprehensive treatise on the nature of the soul, its origin, and its relationship with the body. Ibn Qayyim explores various aspects of the soul, including its existence, types, and states, drawing from Islamic theology, philosophy, and mysticism.