8:5-13 As far as the gospel prevails, evil spirits are dislodged, particularly unclean spirits. All inclinations to the lusts of the flesh which war against the soul are such. Distempers are here named, the most difficult to be cured by the course of nature, and most expressive of the disease of sin. Pride, ambition, and desire after grandeur have always caused abundance of mischief, both to the world and to the church. The people said of Simon, This man is the great power of God. See how ignorant and thoughtless people mistake. But how strong is the power of Divine grace, by which they were brought to Christ, who is Truth itself! The people not only gave heed to what Philip said, but were fully convinced that it was of God, and not of men, and gave up themselves to be directed thereby. Even bad men, and those whose hearts still go after covetousness, may come before God as his people come, and for a time continue with them. And many wonder at the proofs of Divine truths, who never experience their power. The gospel preached may have a common operation upon a soul, where it never produced inward holiness. All are not savingly converted who profess to believe the gospel.
9-13. used sorcery—magical arts.
some great one … the great power of God—a sort of incarnation of divinity.