Adam Clarke on 2 Timothy 3:5

Having a form of godliness - The original word μορφωσις signifies a draught, sketch, or summary, and will apply well to those who have all their religion in their creed, confession of faith, catechism, bodies of divinity, etc., while destitute of the life of God in their souls; and are not only destitute of this life, but deny that such life or power is here to be experienced or known. They have religion in their creed, but none in their hearts. And perhaps to their summary they add a decent round of religious observances. From such turn away - not only do not imitate them, but have no kind of fellowship with them; they are a dangerous people, and but seldom suspected, because their outside is fair.