Charles Ellicott Commentary Matthew 12:26

"and if Satan casteth out Satan, he is divided against himself; how then shall his kingdom stand?" — Matthew 12:26 (ASV)

If Satan cast out Satan — In the Greek, the name has the article in both places, pointing to the one great adversary. It is not that one Satan casts out another, but that he, on the assumption of the Pharisees, casts out himself. Satan is not personally identified with the demon (the deaf or dumb spirit that possessed the man), but the language implies that where evil enters the soul, Satan enters also . There is, as it were, a seeming ubiquity, a solidarité, in the power of evil, just as there is admittedly in the sovereign power of good.