When religious communities adopt secular frameworks, they often unknowingly dismantle their own theological foundations. The transformation of Christmas from a sacred celebration into a cultural holiday and the reconceptualization of "Israel" from a divine covenant into an ethnic identity reveal how secularization operates from within faith traditions themselves. Through comparative religious analysis and historical-theological investigation, this research traces how supernatural religious categories become redefined as ethnic and cultural designations. As post-Enlightenment Jewish communities developed secular forms of identity, they generated what can be termed a "Judaism of Holocaust and Redemption," privileging ethnic survival over religious conviction. The accommodation of secular categories like race and ethnicity triggers a process of self-secularization, where divine imperatives gradually transform into cultural customs. Monotheistic religions—Judaism, Christianity, and Islam—inherently resist such ethnic and racial categorization by establishing transcendent communities based on faith rather than biological inheritance. Yet when these traditions are instrumentalized for secular ethnic continuity, they lose their distinctive transformative power, demonstrating that religion functions as an independent variable that cannot be reduced to a cultural preservation tool without fundamental distortion.