The journalist Lesley Hazleton says that early sources on the prophet Muhammad are infuriatingly vague. He’s described as “neither tall nor short,” “neither dark nor fair,” and “neither thin nor stout.” Hazleton, a longtime Middle East reporter and an agnostic Jew, wanted to understand the man whose legacy continues to shape our world. Her new biography is called “The First Muslim,” and Tuesday, she joins Doug to explain how a man from humble beginnings rose to be the voice and leader of his people.