“The contrast Paul is drawing must not be overlooked. He is not comparing, say, tanks, rifles, and missiles with prayer, fasting, and preaching. The fleshly or worldly side of the contrast depends on the interpretation of 2 Corinthians 10:3-4a – worldly weapons in this context are the kinds of tools of the trade relished by the intruders: human ingenuity, rhetoric, showmanship, a certain splashiness and forwardness in spiritual pretensions, charm, powerful personal charisma. Such weapons they will not find in Paul’s arsenal, so they think him inferior; but Paul responds by openly disavowing such weapons. He would not want to defend himself on that score, for his weapons are of an entirely different sort. They are spiritual weapons, and they are divinely powerful”
Don Carson