2 Timothy 3:5
Form of godliness .. = a form, "people who went under the name of Christ" (Lipscomb); Outsiders are not primarily in view here, but those who had a form of godliness.
Denying the power .. = the implication of this passage is that there is a power in the form of godlienss. The admonition here is not to leave off the forms of the gospel, but not to deny the power of them through godless living.
The power = the false teachers held to a form but were not living the Christian life. What gives power to the form, is the life that is lived.
From such turn away = Avoid, have nothing to do with them. Alford says "This command shows that ...the symptms of the last times were already present." (Lipscomb saw here reasons for withdrawal of fellowship.)