Adam Clarke on Mark 5:9

Legion: for we are many - Could a disease have spoken so? "No, there was no devil in the case; the man spoke according to the prejudice of his countrymen." And do you think that the Spirit of God could employ himself in retailing such ridiculous and nonsensical prejudices? "But the evangelist gives these as this madman's words, and it was necessary that, as a faithful historian, he should mention these circumstances." But this objection is destroyed by the parallel place in Luke, Luk 8:30, where the inspired writer himself observes, that the demoniac was called Legion, because many demons had entered into him.