By the law of faith
Paul means
the principle of justification by faith, as opposed to works; or
considering the Mosaic law through the lens of faith.
We can understand what Paul means by the law of faith
on the basis of two observations. First, Paul has strongly contrasted justification by faith with justification by works of the law. That is, Paul has made clear that one is unable to perform the requirements of the law because of sin, which is why we will never be justified by works of the law. Instead, we are justified by faith in Jesus Christ. Thus, our boasting is excluded by the law of faith, because we do not count on works in which we boast when we are justified by faith. In Paul’s letter to the Galatians he refers to the law of Christ, while in Corinthians he refers to being in-lawed to Christ. What Paul has in mind by these phrases is something like the principles of the gospel as taught by Christ. Likely, Paul has the same idea in mind when he refers to the law of faith in Romans 3:27.
Some contend that when Paul refers to the law of faith, he has in mind viewing the Mosaic law through the lens of faith. That is, Paul is saying that one could view the Mosaic law through the lens of works, or one could view it through the lens of faith. Viewing the law through the lens of works does not exclude boasting, while viewing the law through the lens of faith does.
The problem with this view is that Paul has made clear that righteousness by faith is apart from the law. That is, the law is a set of prescriptions, but because we are not able to uphold them, we need a whole new means of justification. Thus, boasting is excluded, not by looking at the law in a new way, but by forgoing justification by works and holding to faith in Jesus Christ. Further, we know Paul has this contrast between faith in works in mind because in Romans 4:1–5, Paul will say that Abraham is not justified by works, for then he would have something to boast about. Rather, he is justified by faith. There, Paul has in mind the same theme of the law of works and the law of faith, but he is not saying Abraham is justified because he views the law in a new way. For at the time, there was no Mosaic law. The point is that Abraham is justified by faith, not works.
So when Paul refers to the law of faith
he has in mind that boasting is excluded because we cannot earn our salvation but are justified through faith in Jesus Christ.
Interpretation 1:
The law of faith
means the principle of justification by faith as opposed to works.
Summary:
Paul has explained that we all fall short of God’s glory due to sin, which is why God justifies us by his grace through faith in Jesus Christ. Of course, the gospel excludes boasting because we are only right before God on the principle that God justifies us through faith.
According to the law of faith, God reconciles us by grace through faith in Jesus Christ. To acknowledge the law of faith is to acknowledge that one brings nothing to his own salvation. Rather, we come to God, in faith, with an empty hand, and he fills us with Jesus Christ.
Advocates:
Richard Longenecker
Douglas Moo
Frank Thielman
Minor differences:
Our authors agree that when Paul refers to the law of faith, he has in mind that justification is through faith, not works.
Arguments
Possible weaknesses
Interpretation 2:
The law of faith means considering the Mosaic law through the lens of faith.
Summary:
Paul explains that our boasting before God is excluded. Now, it is not excluded by treating the law as a set of prescriptions that one could uphold to be justified before God. Rather, it is excluded by the fact that when one views the law from the perspective of faith, one recognizes God’s grace.
Advocates:
Brendan Byrne
James Dunn
Leon Morris
Minor differences:
Our authors agree that when Paul refers to the law of faith, he has in mind viewing the Mosaic law through the lens of faith.
James Dunn explains the view as follows. He says that when Paul contrasts the law of works with the law of faith, he has in mind that the law should not be understood in terms of a set of prescriptions, such as circumcision and dietary restrictions that must be obeyed. Rather, the Mosaic law must be understood through the lens of faith. When the Mosaic law is understood through the lens of faith, the distinctively Jewish items are not prioritized, which allows for the Gentiles to be included.7
Brendan Byrne agrees that Paul is saying we ought to view the law through the lens of faith, not works. Still, his view is slightly different from Dunn. For Bryne, to view the law through the lens of faith is to view the law as a set of prescriptions one performs in order to become righteous. On the other hand, to view the law through the lens of faith is to see oneself as a total failure to be right in the sight of God.8 When the law is read through the lens of faith, one is led on a different path to righteousness.
Arguments
Possible weaknesses
27 Then what becomes of our boasting? It is excluded. By what kind of law? By a law of works? No, but by the law of faith.