4 You are severed from Christ, you who would be justified by the law; you have fallen away from grace. (RSV)
Cait: Paul here mentions the possibility that those who are in a state of grace can fall away from grace. In this case, it is because they have turned away from the true gospel to the gospel of the Judaizers. In verse 19-21 he goes on to warn them of many other sins which can keep them from inheriting the kingdom. He does not seem to have a “once saved always saved” mindset here.