For he said (elegen gar). For he had been saying (progressive imperfect). Jesus had already repeatedly ordered the demon to come out of the man whereat the demon made his outcry to Jesus and protested. Matthew 8:29 had "before the time" (pro kairou) and Matthew 8:31 shows that the demons did not want to go back to the abyss (thn abusson) right now. That was their real home, but they did not wish to return to the place of torment just now.