The theory of Lakla and Mofe, by creating a new and systematic conceptual model, provides the possibility of a deeper analysis of social and political phenomena and will be an efficient tool for examining discursive actions and structures. The present study analyzes the critical discourse of two sermons of Imam Sajjad (AS) in Kufa and Sham. The main goal is to analyze the formation, structure and discursive consequences of these enlightening sermons using the theoretical framework of Lakla and Mofe. His sermons contain deep political, social and moral themes that, in the historical and social context of that era, played a significant role in revealing the truth and explaining the position of the Ahl al-Bayt (AS). The present research method is qualitative and based on the analysis of the documentary and textual content of the sermons. In this regard, the key concepts of Laclau and Mouffe's theory, including "central sign", "hegemony", "deconstruction", "discursive moments", etc., have been used to examine how the discourse of resistance and justice confronts the dominant and oppressive discourse of the time. The analyses show how Hazrat Sajjad (AS), using rhetorical tools and effective discourse strategies, was able to preserve and convey the message of Ashura, awaken the conscience of society, and restore the delegitimized credibility of the Prophet's family (PBUH). These sermons, not only in their time, but also throughout history, have served as a platform for a deeper understanding of the Karbala event and the fight against oppression and corruption.