Bible Verses About Backsliding: Is departing form the simplicity of the gospel

O senseless Galatians, who hath bewitched you that you should not obey the truth: before whose eyes Jesus Christ hath been set forth, crucified among you?

This only would I learn of you: Did you receive the Spirit by the works of the law or by the hearing of faith?

Are you so foolish that, whereas you began in the Spirit, you would now be made perfect by the flesh?