Geerhardus Vos ('The Doctrine of the Covenant in Reformed Theology,' in Shorter Writings of Geerhardus Vos, 234, fn1):
(Ibid., 255, fn1):
With respect to the covenant of grace, the distinctively Lutheran view comes out in the fact that nothing but faith was recognized as the condition of the covenant (stipulatio foederis). Reformed theologians also add to this, without hesitation, new obedience, and say that justification is by faith alone but that the covenant is much broader. The Lutheran brings the sole fide from justification to the idea of covenant when he takes up the latter.
(Ibid., 255, fn1):
The law holds an essentially different place for the Lutherans than for the Reformed. Theoretically both agree in the threefold use of the law: usus politicus, usus elenchticus, usus normativus (i.e., (1) the law as the rule of civil righteousness; (2) the law as pedagogue leading to Christ; (3) the law as rule of life for the regenerate). The dififrence lies in the fact that the Lutherans only relate this third useof the law to the remnants of the old nature of the believer, while the Reformed relate it to the new man, who finds in the law a positive rule of life.