The Fadak Sermon is a foundational text of early Islam in which speech functions not merely as a legal claim but as a discursive act that reconstructs the criteria of truth, justice, and legitimacy. Existing studies have largely examined the sermon within the historical dispute over Fadak or as a theological rhetorical text, giving limited attention to how it redefines the very standards by which political and legal legitimacy are judged. This study addresses this gap by examining the logic through which “truth” and “legitimacy” are articulated in the discourse of the Fadak Sermon.

Employing a qualitative analytical approach, the research draws on van Dijk’s cognitive-oriented critical discourse analysis, together with Laclau and Mouffe’s theory of hegemony and articulation and Bourdieu’s concept of symbolic capital. The corpus consists of the full text of the Fadak Sermon and syntactically and semantically parallel Qurʾanic verses. Analysis is conducted across linguistic, cognitive, and socio-power levels.

The findings show that in the discourse of the Fadak Sermon, monotheism (tawḥīd) operates as a prior cognitive-political criterion for judging justice and legitimacy rather than as a purely doctrinal belief. By articulating concepts such as truth, justice, and obedience around the central signifier of monotheism, legitimacy is constituted as symbolic capital whose validity depends on alignment with the divine order. The article’s main contribution lies in proposing a concise analytical model for understanding the discursive production of legitimacy in religious-political texts without reducing them to political prescriptions or purely historical interpretations, while clarifying mechanisms of authority, judgment, and normative evaluation.