Materiality has been largely left out of the study of Muslim life in Europe, and limited to an etic rather than emic approach. In this paper, I analyse a conservative London mosque community (the East London Mosque) that depends on the material––what I term “ethical substance”––to reinforce its ascetic rejection of the world. Drawing from five months of ethnographic research in this mosque, I examine three aspects of materiality––clothing, the mosque building, and technology––in order to explore how the community negotiates its position in the city at hand, as well as more broadly vis-à-vis modernity. The mosque emerges as a site of discursive-material tension where ethics and locale intersect, and where intention (niyya) matters more than the constitution of objects. It elucidates European modernity as broader than liberal democratic ideals (i.e. in a community stressing a returns towards, rather than away from, tradition).