Linguistic antonymy represents one of the most prominent semantic mechanisms in Arabic, playing a pivotal role in expanding semantic horizons and transcending the fixed central denotations of lexical items. This study investigates this phenomenon within al-Ṣaḥīfa al-Kāẓimiyya, treating this devotional corpus as a distinctive model of religious discourse that harnesses linguistic opposition to convey complex direct and indirect messages. Employing a descriptive-analytical method, the research tracks these oppositions throughout the supplications of the Ṣaḥīfa, underscoring the decisive function of linguistic context in steering signification and shaping counterpositional meaning. The significance of this study lies in elucidating the structural diversity of these antonymous configurations; rather than being confined to isolated lexical oppositions (al-ḍiddiyya al-mufrada), they encompass complex syntactic antonymies (al-ḍiddiyya al-murakkaba) operating across clauses and phrasal structures, thereby reinforcing the text’s semantic density and rhetorical vigor. Furthermore, the study classifies these structures thematically into doctrinal, ethical-axiological, and existential dyads concerning the Divine Attributes and the servant–Creator relationship. The findings demonstrate that the deployment of antonymy in al-Ṣaḥīfa al-Kāẓimiyya constitutes an intentional semantic strategy designed to consolidate core theological concepts and introduce layered interpretative dimensions. Moreover, the analysis identifies multipartite “dual antonymies” (taḍādd muzdawij) in specific prayers such as Duʿāʾ al-Jawshan al-Ṣaghīr, opening new perspectives for linguistic inquiry into devotional discourse and confirming that antithetical structures serve as foundational elements in constructing sacred texts and heightening their affective impact on the reader.