The Apostle Paul twice cites Leviticus 18:5 in the midst of important arguments about justification.
In Galatians 3:12 he says, “But the law is not of faith, rather ‘The one who does them shall live by them.'”
And in Romans 10:5 he says, “For Moses writes about the righteousness that is based on the law, that the person who does the commandments shall live by them.”
One of the more common recent readings is that Paul is not talking about the actual Mosaic law, but rather about a legalistic misuse or misunderstanding of it. In part this is because we know that salvation has always been by faith, even under the Mosaic covenant, and yet Paul appears to be contrasting the law with faith (see Gal. 3:11 and Rom. 10:6 for the contrasts).
However, this “misuse of the law” interpretation simply can’t account for Paul’s actual flow of thought and argument. Tom Schreiner points out one of the reasons in 40 Questions About Christians and Biblical Law: “the misinterpretation view suffers from a major defect. Elsewhere Paul always cites an Old Testament text positively to advance his own argument, and we are lacking any clear evidence that he responds to a wrong understanding here. It is most likely, then, that Paul cites the Old Testament to advance his argument.”
So what is Paul really doing? I think Schreiner’s understanding is exactly right, and if you don’t see Paul’s strategy here, you’ll misread a good chunk of Paul’s contrast between the old and new covenants.
Paul reads Leviticus 18:5 redemptive-historically.
Perfect obedience is demanded from those who place themselves under the law, for the atonement provided by Old Testament sacrifices no longer avails with the coming of Christ.
Perfect obedience was not demanded in one sense under the Sinai covenant, for the law provided forgiveness via sacrifices for those who transgressed.
In Paul’s view, however (see Gal. 3:15-4:7), the Sinai covenant is no longer in force. Hence, those who observe circumcision and the law to obtain justification (Gal. 5:2-4) are turning back the clock in salvation history. The coming of Christ spells the end of the Sinai covenant (Gal. 3:15-4:7). Hence, those who live under the law must keep it perfectly to be saved, for in returning to the law they are forsaking the atonement provided by Christ (Gal. 2:21; 5:3). Returning to the law is futile, however, for the sacrifices of atonement under the Sinai covenant pointed ahead to the sacrifice of Christ. Therefore animal sacrifices no longer provide forgiveness now that the definitive sacrifice of Christ has been offered (Gal. 3:13).
In the chapter on this verse in his book, Dr. Schreiner also explains what Leviticus 18:5 meant in its original context, how it was interpreted in the rest of the OT, and why we should reject the reading that sees Romans 10:5 and 10:6-8 as both describing the life of faith.
