Qiṣāṣ (retributive punishment), as one of the most significant institutions of Islamic and Iranian criminal law, possesses a complex and multi-layered nature and has long been a subject of debate within the realms of legal philosophy and criminology. On the one hand, in Islamic jurisprudence and domestic legislation, Qiṣāṣ is recognized as the “right of retaliation” vested in the victim’s heirs, who hold the authority to either enforce or forgo it; hence, it assumes a private and revenge-oriented character. On the other hand, in its public and religious dimension, Qiṣāṣ is not merely a license for retaliation but a divine duty aimed at establishing balance and avoiding excess, signifying its ultimate purpose in moderating violence, ensuring criminal justice, and preserving social order within the framework of divine limits. This conceptual duality between the private right of retaliation and the divine duty of balance and restraint has generated numerous theoretical and practical challenges not only at the conceptual level but also in the functional operation of Qiṣāṣ, particularly in relation to deterrence theory, the tension between individual interests and collective welfare, the limited role of state authority in the implementation of punishment, and the uncertainty surrounding the ultimate nature of Qiṣāṣ within Iran’s criminal policy. This tension provides a platform for analytical and descriptive inquiry based on Islamic jurisprudential and legal sources, in order to explore the foundations of this duality and its reflections on deterrence theory. The research findings indicate that reducing the institution of qisas from a “divine obligation to uphold justice and proportionality” to merely a “private right of the heirs of the victim” undermines the divine and social foundations of criminal justice and diminishes its deterrent effect....