Matthew 12:26

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."

In this chapter, we have, I. Christ's clearing of the law of the fourth commandment concerning the sabbath-day, and vindicating it from some superstitious notions advanced by the Jewish teachers; showing that works of necessity and mercy are to be done on that day (Mat 12:1-13). II. The prudence, humility, and self-denial of our Lord Jesus in working his miracles (Mat 12:14-21). III. Christ's answer to the blasphemous cavils and calumnies of the scribes and Pharisees, who imputed his casting out devils to a compact with the devil (v. 22-37). IV. Christ's reply to a tempting demand of the scribes and Pharisees, challenging him to show them a sign from heaven (Mat 12:38-45). V. Christ's judgment about his kindred and relations (Mat 12:46-50).

12:26 Jesus argued, in essence, “If I cast out demons under the influence of Satan, then Satan is dividing his camp, which obviously would be a foolish thing for Satan to do.”