This research was conducted with the aim of providing a philosophical explanation of the mechanism by which repentance purifies the sinful soul within the intellectual system of Mulla Sadra. The main question is how, given the acceptance of the union of act and agent (i.e., the identity of sin with the essence of the sinner), repentance can purify the contaminated essence without annihilating the individual's personal identity. The innovation of the research lies in the systematic application of the principles of the primacy of existence (asālat al-wujūd), the gradation of existence (tashkīk al-wujūd), the principle of the flow of existence (qā'idat al-saryān), and substantial motion to address this challenge.The findings indicate that repentance is a strong existential attention towards the most perfect level of existence (God), which, in the voluntary process of the soul's substantial motion, creates a new and more intense existential reality for the soul. This stronger existential reality, according to the principle of the flow of existence, absorbs and nullifies the weaker existential reality resulting from sin. In this process, personal identity (which is the continuous existential relation and attachment of the soul to God) remains constant, but the existential reality of the soul (its level and quality of existence) undergoes a substantial transformation from a state of degradation towards luminosity and purity. Therefore, in transcendent philosophy , repentance is not a conventional matter but rather an ontological transformation that reconstructs the essence of the soul, and it remains possible until the final moments of worldly life.