Gal. 5:3 And I testify again to every man who receives circumcision, that he is under obligation to keep the whole Law.
Not only will Christ not allow himself to be joined to human self-righteousness, but the Apostle makes sure everyone understands that there is no such thing as partial righteousness in the law: one either follows the whole of the law (leading inevitably to condemnation) or one does not head down that path at all. The path of grace is 180 degrees separated from the path of law: one cannot travel down both very far. But again, if the error of the Judaizers in Galatia was, in fact, that they were denying Christ’s role as suffering Messiah, and insisting upon fulfillment of the law as the means of righteousness, why would Paul speak as he does here? Obviously, his opponents were not presenting a “pure law” perspective, but were instead, as we see by comparing the statements of verses two and three, presenting a synergistic combination of the work of Christ and the fulfillment of legal requirements. Paul’s point is simple: it is either one or the other, there can be no mixture. If you choose the path of grace in Christ, you cannot join anything to that path; if you choose the path of legal fulfillment, you must stay that course. Grace allows for no meritorious fulfillment of law, and law allows for no relaxation of its standards by grace. The two are mutually exclusive concepts, as Paul makes clear.
Gal. 5:4 You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace.
Once again the Apostle’s words make sense only if we recognize what has come before: if these Judaizers had denied the centrality of the sacrifice of Christ and were simply promoting a works-fulfillment scheme, whether you see this as involving signs of national identity or works of meritorious righteousness in the law, Paul’s words are nonsensical if they were not in fact speaking of the centrality of Christ and the necessity of grace. He speaks of being severed from Christ: why would this matter to one who sees Christ as an auxiliary, secondary aspect? Obviously, the Judaizers were claiming to be in Him, so that to be severed from Him would be a strong rebuke. They were obviously likewise claiming to rely upon grace in some form, for if they were not, why tell them they were fallen from it? When Paul speaks of those seeking to be justified by law, he is not repeating their own phraseology, he is giving his own evaluation of their synergistic joining of law fulfillment (circumcision) with their proclaimed faith in Christ. Someone who would openly advocate legal fulfillment of the law as the means of a right standing before God would find Paul’s rebuttal humorous, for it would only have impact upon someone claiming to be in Christ and to be dependent upon grace.