Starting from the polemics of the Ibādī mufti of Oman, Ahmad al-Khalīlī, with Ibn Bāz and other Wahhābī 'ulamā' this paper addresses how representatives of contemporary Islam try to overcome sectarian differences and how they make sense of medieval theological precepts in a radically changed intellectual and political environment. The paper stresses the role of (invented traditions of) resistance against external and internal foes (imperialism and—to a lesser degree—Sufism) as ideological basis for modernist Islamic ecumenism. Remaining sectarian differences are explained by pretending that rival sects are in reality agents of external enemies of Islam. An example of this argumentation is Ahmad al-Khalīlī's effort to remove the Wahhābīs from the fold of Islam by making Wahhābism a Jewish sect with Islamic trappings. For this purpose Ahmad al-Khalīlī recycles premodern Ibādī polemic against the Sunnis at large. Medieval theologoumena are thereby given a present-day political meaning. Without openly attacking the Sultan, the mufti al-Khalīlī's arguments against the Wahhābīs can at the same time be read as a document of opposition against the Omani regime's policies, in a situation where the Sultanate is confronted by a resurgence of political Ibādism.