At the heart of the $2 trillion Islamic-finance industry is a ban on interest. But why is there only anIslamicban on interest today? After all, for over a millennium, interest was also gravely sinful in Judaism and Christianity. While scholars have addressed the evolution of Jewish, Christian, and Islamic economic morality in isolation, very few since Weber have tackled the interest question directly and comparatively.I argue that the fate of the religious interest ban has always depended on the fate of religious jurists. When religious jurists are absent, no systematic interest ban emerges. When religious jurists emerge as technical experts, the interest ban appears and thrives. And when religious jurists come under attack or lose their traditional role in society, the interest ban withers and dies.To conclude, I call for a reconstruction of Weber’s theory of religion and economic morality that dissolves the tradition-modernity binary.