"While there are hundreds of sources for militant, or lesser, jihād in classical Islam—hadīth collections, commentaries on the Koran, law books from all the schools of law, and so on—there do not seem to have been any works devoted exclusively to spiritual, or greater, jihād. This is clearly a derivative form, since it is not mentioned in any of the canonical collections of hadīth. Even the later literature on jihād fails to mention “greater jihād.”"