Using lectures, pamphlets, and newspaper articles, I examine a debate among Muslim scholars in the Levant in the 1920s and 1930s on the permissibility of the family waqf [endowment]. While the question rose to prominence because of wider shifts in notions and practices of charity, property, and economy, the debate was centered on legal reasoning and the place of texts in justifying the ruling [hukm] on the family waqf. The main question debated was whether the widespread Islamic family waqf was part of “religion.” Focusing on scholars opposed to the family waqf, I describe their arguments that the family waqf was not a “religious” endeavor and hence did not need to follow “religious law.” Instead, they proposed that the family waqf should follow the new laws of the economy. Because family waqfs appeared to harm the economy, the Islamic legal ruling on family waqfs ought to be changed from recommended to reprehensible or prohibited in order to avoid harm, based on the Islamic legal maxim that harm should be avoided. This argument, I contend, shows a rearticulation of the Islamic legal tradition with a new field conceived to be outside of “religion” and having its own rules: the economy. I argue that changing the ruling concerning the family waqf on the legal plane became possible through the introduction of a new statistical style of reasoning within the Islamic legal tradition. Unlike arguments based on analogical reasoning, arguments based on statistical styles of reasoning are presented as objective truths that are not based on textual interpretations, and that do not require any special ethical training in order to be correctly understood and applied. I suggest that introducing such styles of reasoning has had a deep impact on structures of authority in the Islamic legal tradition.