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

O thoughtless Galatians, who did bewitch you, not to obey the truth--before whose eyes Jesus Christ was described before among you crucified?

this only do I wish to learn from you--by works of law the Spirit did ye receive, or by the hearing of faith?

so thoughtless are ye! having begun in the Spirit, now in the flesh do ye end?