The old-school Dutch Reformed divine, Johannes VanderKemp, was a solid defender of the good old Reformation truths – of course, this included justification by faith alone. In a sermon on Romans 3.27-28, he explained the Catechism’s (Q/A 62-64) defense of justification. For VanderKemp, along with many other Reformed and Presbyterian theologians of his day, justification had much to do with a proper understanding of the covenants: works and grace. Here’s one paragraph:
“It appears very plainly, that by these two covenants he (Paul in Gal 4.24ff) understands, (a) the covenant of works, the sum of which, together with the covenant of grace (which was administered in a legal manner under the Old Testament) was proposed at mount Sinai, and often exhibited for the condemnation of sinners, and in order to urge them to the Messiah, who was to come; and therefore the Jews, the Jerusalem of Paul’s time, seeking their righteousness and the inheritance by this covenant, showed that they, being born after the flesh, of the servile covenant of works, were also servile with their children, since they, like Ishmael, mocked and persecuted them, who were born after the Spirit. (b) The second covenant, which Paul mentioneth, is the covenant of grace, which is established only in promises; and therefore all who believe, the Jerusalem that is above, the true church, being born like Isaac, after the Spirit, of this covenant, are free, and obtain the inheritance by promise” (vol 1, p. 433 of The Christian: Entirely the Property of Christ in Life and Death by Vanderkemp).
Though the Reformed were not exactly in agreement with every point concerning the covenants and how they were “found” in the Mosaic administration, there was a general consensus on the definitions and affirmations of the covenants (works and grace).
If you want more info on this, you’ll have to check out this one and this one, among others. Also, we’ve posted on this before, so if you want more info, check our covenant tags, or justification tag, or do a search.