Water has a vital role in human life, as the source and symbol of life, particularly in the Islamic community. Poor management of water resources in recent decades has posed a serious threat to the physical aspect of life in Islamic countries, which are predominantly located in dry regions. Moreover, the weakness of functional and symbolic position of water in Islamic-Iranian architecture has been the consequence of this situation. Water have a tangible and essential role not only in the physical aspect of human life (external world), it is also closely connected with the spiritual aspect of life (inner world), assisting individuals in stages of felicity (sa'adah) and perfection (kamal) according to transcendent theosophy. With its richness linked with spiritual, sacred, and mystical manifestations, Islamic architecture represents water both in its external world (zahir) and inner world (batin). In terms of the former,issue water unites with the real space for the purposes of balancing and regulating the climate conditions; in terms of the latter, issue it merges with the sacred atmosphere of the architecture. Therefore, water is one of the most valuable, universal, and structural elements of Islamic architecture. In Mulla Sadra’s view, water can be considered as one of the symbolic cores of perfecting motion of life with regard to his doctrine of substantial motion. The Holy Quran mentions different forms of the role of water in witnessing and being of humanities more than 63 times. The manifestations of such intuitive quantitative instances were studied based on the stages of Sadrai perception, namely the sensory, the imaginary, and the intellectual. As shown in the theoretical framework, this analysis revealed the generalizability of universal vital, sacred, biological, and technological values to architecture and urban spaces. Accordingly, beauty, vitality, and life in the general sense and life in the sense of becoming Godliness were the ultimate findings of studying the function of water in Islamic architecture.