Matthew Poole and continuators on Galatians 5:4

4 Christ is become of no effect unto you, whosoever of you are justified by the law , ye are fallen from grace .

The word here translated, become of no effect is used Rom. 3.3. By those, who are justified by the Law, are to be understood such as seek, or desire to be justified by the Law, for actually none is so justified. The sense is, who ever seeketh to be justified by the works of the Law, he disclaimeth the righteousness of Christ; to him Christ's death signifieth nothing, nor is of any vertue at all: For he had told us before, chap. 2.21. If righteousness were by the Law, then Christ is dead in vain, and Rom. 8.3. What the law could not d in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin condemned sin in the flesh, that the righteousness of the law might be fulfilled in us, &c. The very end of Christ's coming and dying was to supply us with a righteousness, which (apprehended by Faith) should be reckoned to us as ours; wherein we might stand before God. Which end of Christ's Death had been frustrated, if through our flesh, there had not been such a weakness, or impotency in the Law as to Justification. So as if any still looked for Justification by performance of the Law, as such, made the death of Christ in vain, because if such a thing could have been done that way, there had been no need of Christ's dying: So they also made it, which was not in vain in it self, yet in vain, and of no effect to their Souls; because Christ would not be a partial cause in the Justification of a Soul.

And they, by this renounced the Grace of God exhibited in the Gospel, and fell from the grace of it. For by Grace here is not to be understood, a state of grace, (from which none can fall totally and finally,) but the Grace of the Gospel; by which is signified the free love of God in it exhibited, offering Christ to sinners for Righteousness.