This paper examines Mosaic betrothal as an institutional mechanism that structured social hierarchies and inequalities. While previous studies have treated betrothal merely as a precursor to marriage, this study uses a Law and Economics framework to analyze betrothal as an independent institution that governs incentives, transaction costs, and the allocation of economic and social risks. Drawing on biblical legal texts and rabbinic interpretations, this paper demonstrates that Mosaic betrothal functioned as a staged commitment device. Its structure increased exit costs over time and, under certain conditions, redistributed risk toward protecting the more vulnerable party. A formal microeconomic and game-theoretic model further indicates that requiring a formal writ for dissolution ostensibly yields a higher social surplus than regimes permitting low-cost exit, despite some sensitivity to external factors. These findings complicate conventional interpretations of Mosaic law as either purely oppressive or purely protective. Instead, Mosaic betrothal emerges as a dual institution. It materially reproduces gendered inequality through asymmetric obligations, yet simultaneously mitigates its most destabilizing effects through legal safeguards, reputational constraints, and enforced commitment. In this framework, religion operates not only as a cultural superstructure but also as a mechanism for embedding and stabilizing economically efficient yet normatively ambivalent arrangements of inequality. By bringing the incentive-based logic of betrothal to the foreground, this research contributes to broader debates on how religious legal systems produce, naturalize, and occasionally restrict inequality. It also introduces Law and Economics as a complementary analytical lens for theological and socioreligious inquiry. The research provides a structured explanation of how legal forms, economic rationality, and moral norms evolve together in the governance of intimate life.