Drawing on archival and ethnographic research in Lebanon and Turkey, this dissertation investigates changes in the conception and practice of Islamic charitable endowments – called waqfs – in Beirut since 1826. In French Mandate Lebanon (1920-1943), a new question about charity emerged: how was one to distinguish when a charitable endowment was a truly religious act? I first trace how this question became imaginable starting in the nineteenth century Ottoman Empire, notably through the rise of the modern capitalist state, its monopoly on the production and administration of law, and the creation and separation of the spheres of religion and economy. I then argue that the selection of religious endowments hinged on new conceptions of the state and general benefit and upon a conception of charity as a practice confined to the public sphere. The answer to this question therefore subjected charitable endowments and their founders to new understandings of charity, property, and intent and redefined the very practice of charitable giving in the Islamic tradition afterwards and up to this day.