And if Satan cast out Satan, he is divided against himself; how shall then his kingdom stand?

People's New Testament

12:26 If Satan cast out Satan. If demons were cast out by the aid of Satan, then Satan was fighting against his own servants. His kingdom was divided against itself.

Wesley's Notes

12:26 How shall his kingdom be established - Does not that subtle spirit know thin is not the way to establish his kingdom?

Jamieson-Fausset-Brown Bible Commentary

26. And if Satan cast out Satan, he is divided against himself; how shall then his kingdom stand?-The argument here is irresistible. "No organized society can stand-whether kingdom, city, or household-when turned against itself; such intestine war is suicidal: But the works I do are destructive of Satan's kingdom: That I should be in league with Satan, therefore, is incredible and absurd."

Matthew Henry's Concise Commentary

12:22-30 A soul under Satan's power, and led captive by him, is blind in the things of God, and dumb at the throne of grace; sees nothing, and says nothing to the purpose. Satan blinds the eyes by unbelief, and seals up the lips from prayer. The more people magnified Christ, the more desirous the Pharisees were to vilify him. It was evident that if Satan aided Jesus in casting out devils, the kingdom of hell was divided against itself; how then could it stand! And if they said that Jesus cast out devils by the prince of the devils, they could not prove that their children cast them out by any other power. There are two great interests in the world; and when unclean spirits are cast out by the Holy Spirit, in the conversion of sinners to a life of faith and obedience, the kingdom of God is come unto us. All who do not aid or rejoice in such a change are against Christ.