Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

"And righteousness will be to us, if we observe to do:" i.e., our righteousness will consist in the observance of the law; we shall be regarded and treated by God as righteous, if we are diligent in the observance of the law. "Before Jehovah" refers primarily, no doubt, to the expression, "to do all these commandments;" but, as we may see from Deu 24:13, this does not prevent the further reference to the "righteousness" also. This righteousness before Jehovah, it is true, is not really the gospel "righteousness of faith;" but there is no opposition between the two, as the righteousness mentioned here is not founded upon the outward (pharisaic) righteousness of works, but upon an earnest striving after the fulfilment of the law, to love God with all the heart; and this love is altogether impossible without living faith.