Before he founded Jews for Jesus, Moishe (at the time, Martin) Rosen took business classes and sold fishing rods. Taking employment at a sporting goods store rather than at his father’s junkyard was Rosen’s first rejection of his ancestral legacy, his first apostasy. But his sales career — later he also sold cameras and cemetery plots — foreshadowed something beyond a simple conversion to Christianity. According to a new biography by his daughter, Ruth Rosen, the famous evangelist never really left sales.

The business classes Rosen took at the Emily Griffith Opportunity School, a technical school in Denver, seem to have influenced his career as a “fisher of men” far more than his theological education at Northeastern Bible Institute...