John Calvin on the Covenant of Works & Grace
The following is an excerpt from Calvin's concise summary of the Christian faith for ordinary people entitled Truth for all Time.
When he taught that the whole law is contained in two articles, our Lord Jesus Christ declared to us clearly enough what is the real purpose of all the commandments of the Law. The first article is that we should love the Lord, our God, with all our heart, with all our soul and all our strength. The second article is that we should love our neighbor as much as we love ourself. And he has taken this interpretation from the Law itself, for the first part is found in Deuteronomy 6:5, and we see the other in Leviticus 19:18. There, then, is the standard and pattern of a holy and righteous life, and even a most perfect picture of righteousness; so that if someone expresses the Law of God in his life, he will not lack before the Lord anything of what is required of perfection. To bear this out, the God promises to those who will have carried out his Law not only the great blessings of the present life which are referred to in Leviticus 26:3-13 and Deuteronomy 28:1-14, but also the reward of eternal life (Lev. 18:5).
On the other hand, God announces the retribution of eternal death for those who will not have accomplished by their deeds all that is commanded in this Law (Deuternomy 28:15-68). Also Moses, having made the Law known, takes heaven and earth to witness that he has just put before the people good and evil, life and death (Deut 30:19-20). But although the Law shows the path ot life, yet we have to see how it can benefit us. Of course, if our will were fully trained and disposed to obey God's will, just to know the Law would be more than enough to save us. As it is, however, our carnal and corrupt nature fights all the time, and in every way, against the Spiritual Law of God. The teaching of this Law does not improve our nature in any way at all. so it is that this same Law (which was given for salvation if it found hearers who were good and capable of keeping it) turns into something which results in sin and death. For since we are all convicted of being transgressors of the Law, the more clearly the Law reveals to us the righteousness of God, the more clearly, on the other hand, it uncovers our unrighteousness. Consequently, the more the Law catches us going further into transgression, the heavier will be the judgment of God of which it finds us guilty. The promise of eternal life being removed, all that remains for us is the curse which, by the Law, falls on us all.
The evidence given by the Law prooves the unrighteousness and transgression of all of us. Its purpose in this, however, it not that we might fall into despair nor, being totally discouraged, that we should founder in ruin. Admittedly, the Apostle testifies that we are all condemned by the Law's judgment, so that every mouth may be closed and the entire world be found guilty before God (Rom 3:19). However, he himself teaches elsewhere that God has imprisoned all men under the power of unbelief, not in order to ruin them or let them perish, but that he might have mercy on all (Rom 11:32). Having then used the Law to tell us of our weakness and impurity, the Lord comforts us through trust in his power and mercy. And it is in Christ, his Son, that he reveals himself as being benevolent and favourably disposed to us. In the Law God only appears as the rewarder of perfect righteousness - of which we are completely bereft - and, on the other hand, as the upright and strict Judge of sins, in Christ, his face is full of grace and gentleness, and shines on miserable, unworthy sinners. For this is the admirable display of his infinite love that he gave to us: he delivered up his own son for us and, in Him, opened to us all the treasures of his mercy and goodness.
Excerpt from Truth for all Time by John Calvin