By faith he is a member of the covenant, and that faith has a wide outlook, a comprehensive character, which not only points to justification but also to all the benefits which are his in Christ. Whereas the Lutheran tends to view faith one-sidedly—only in its connection with justification—for the Reformed Christian it is saving faith in all the magnitude of the word. According to the Lutheran, the Holy Spirit first generates faith in the sinner who temporarily still remains outside of union with Christ; then justification follows faith and only then, in turn, does the mystical union with the Mediator take place. Everything depends on this justification, which is losable, so that the believer only gets to see a little of the glory of grace and lives for the day, so to speak. The covenantal outlook is the reverse. One is first united to Christ, the Mediator of the covenant, by a mystical union, which finds its conscious recognition in faith. By this union with Christ all that is in Christ is simultaneously given. Faith embraces all this too; it not only grasps the instantaneous justification, but lays hold of Christ as Prophet, Priest, and King, as his rich and full Messiah.
Geerhardus Vos, Redemptive History and Biblical Interpretation: The Shorter Writings of Geerhardus Vos, ed. Richard B. Gaffin Jr. (Phillipsburg, NJ: P&R Publishing, 2001), 256.