One of the most important effects of marriage is the commitment and fidelity of each spouse to the other. Alongside the obligations arising from marriage, sexual fidelity may be regarded as one of the most important of these obligations, as it constitutes, in essence, the foundation of married life. Although the criminal aspects of violating this obligation, as well as its effects on the spouses’ financial relations, such as maintenance, have consistently been emphasized by Islamic jurists and legal scholars, the issue of spousal infidelity and its impact on the marriage contract and the obligations of the parties still warrants further examination and discussion.

The present study, in addition to examining the various forms of criminal remedies, analyzes the civil remedies applicable to this issue, drawing upon jurisprudential sources and elucidating its theoretical foundations, including the principle of kafā’a (compatibility between spouses) and the identification of its instances, as well as the jurisprudential maxim “lā mahr li-baghy” (no dowry is due for illicit sexual conduct). It further argues that infidelity is, by its nature, a contractual breach and a violation of the implicit and foundational condition of fidelity underlying the marriage contract.

Given the significance and, regrettably, widespread prevalence of this reprehensible phenomenon in human societies, including Iranian society, and the serious and sometimes irreparable harm it inflicts upon the family and society as a whole, fidelity cannot be regarded merely as a moral obligation. Through an examination of jurisprudential foundations and texts using a descriptive-analytical method, the present study supports the view that, in addition to the severe criminal penalties applicable to zinā (unlawful sexual intercourse), spousal infidelity may also entail civil legal consequences. By giving rise to legal concepts such as sū’ al-mu‘āshara (marital mistreatment) and nushūz (marital disobedience), infidelity may affect not only the continuation or dissolution