Albert Barnes Commentary Matthew 12:28

"But if I by the Spirit of God cast out demons, then is the kingdom of God come upon you." — Matthew 12:28 (ASV)

But if I—by the Spirit of God, etc. The Spirit of God, here, means the power of God—in Luke, by the finger of God. Compare Exodus 8:19; Psalms 8:3. If this work is not by the aid of Satan, then it is by the aid of God. Then his kingdom, or reign, has come (Matthew 3:2). The reign of Satan over men, and the reign of God, are in opposition. If God expels Satan from his dominion over men, then his reign has come.