Oppression is among the grave sins, and cooperation in oppression is considered—both rationally and according to Islamic law—as a form of oppression, making it subject to the same corresponding rulings. Cooperation in oppression, in its broad sense encompassing participation and assistance, may occur in various forms. Jurists have examined assistance in oppression under the concept of ma‘ūnat al-ẓālimīn within the chapter on prohibited transactions (makāsib al-muḥarramah). Assistance in oppression is forbidden when it constitutes aiding the oppressor in his act of oppression or when it leads to the assistant being characterized as a supporter of a tyrant; according to the purport of certain narrations, such assistance may even entail exclusion from Islam. Participation in oppression results in all participants equally deserving the full punishment designated for that specific act of oppression. Assistance in oppression likewise incurs liability; and aside from specific instances in which mere assistance does not fully actualize the legal designation upon the assistant, wherever assistance in oppression occurs, the assistant is thereby characterized as an oppressor, and the designation of “oppressor” applies to that individual. Thus, in terms of the legal status of “oppressor,” both the direct perpetrator and the assistant share the same ruling and merit equal punishment. This treatise was conducted with the aim of undertaking a jurisprudential analysis of cooperation in oppression against the Ahl al-Bayt (peace be upon them), with special emphasis on the injustices inflicted upon Lady Fatimah (peace be upon her), using descriptive and analytical methods. The findings indicate that, both rationally and legally, the higher the status and rank of the oppressed party, the more reprehensible the act of oppression becomes and the more severe the corresponding punishment ought to be. Since the Ahl al-Bayt, endowed with infallibility and purity, occupy the loftiest ontological rank and the highest degrees of nearness to God and sanctity, the punishment for oppressing them—or cooperating in such oppression—is accordingly more severe. Likewise, the sacred law has deemed insulting them as warranting execution, and enmity toward them as constituting nusb and apostasy. Based on this, all individuals who directly or indirectly participated in the oppression of the Ahl al-Bayt—especially Lady Fatimah—are, if their cooperation in oppression extends beyond inner approval and assent and manifests in overt words or actions, categorized as nāsibī (one who harbors hostility toward the Ahl al-Bayt), thereby falling outside the fold of Islam and deserving the most severe punishment according to the sacred law. However, if such cooperation remains purely internal and has not outwardly manifested, no legal ruling applies to it in this world, although from a spiritual and eschatological perspective such a person is considered a hypocrite.