Of the Law of God
1. God gave to Adam a law, as a covenant of works, by which he bound him and all his posterity to personal, entire, exact, and perpetual obedience, promised life upon the fulfilling, and threatened death upon the breach of it, and endued him with power and ability to keep it.
2. This law, after his fall, continued to be a perfect rule of righteousness; and, as such, was delivered by God upon Mount Sinai, in ten commandments, and written in two tables: the first four commandments containing our duty towards God; and the other six, our duty to man.
CHAPTER 7[WCF 7] - It can be fairly said that upon the fall, the only thing that changed concerning the law was that man was no longer capable of keeping it as a covenant of works? The law as a covenant of works didn't end or change. Rather innocent man had changed and, as a sinner unable to obey, was brought under the curse of that law/covenant of works. In other words, the law/covenant remained in effect.
Of God's Covenant with Man
2. The first covenant made with man was a covenant of works, wherein life was promised to Adam; and in him to his posterity, upon condition of perfect and personal obedience.
3. Man, by his fall, having made himself incapable of life by that covenant, the Lord was pleased to make a second,
[WCF 19] - The moral law given to Adam was given as a covenant of works (LC 93). Upon the fall there is nothing that indicates, either in Scripture or the confession, that the law ceased to still embody the covenant of works. And there isn't anything, is there, that indicates that with the advent of the covenant of grace (protoevangelium and Abraham) that the covenant of works ended? And it was THIS law in section 2 (referring to the law as a covenant of works defined in section 1) that God delivered on Mt. Sinai and yet, though no man could fulfill it, all were and are still obliged to obey it as a perfect rule of righteousness as originally given in the garden.
Now whether one argues that God delivered the law as a rule of righteousness or that he delivered it both as a rule of righteousness and a covenant of works for pedagogical and typological reasons, it seems fair to affirm that the law after the fall was still connected to the covenant of works (LC 93) and as such was present in the Mosaic covenant.
Q. 93. What is the moral law?Isn't that why, when we speak of our justification, we say that we are imputed with Christ's obedience to the law's demand/requirement for perfect obedience? It rightly can be said that we have fulfilled the covenant of works in Christ. Before the law as a covenant of works His obedience is counted as ours.
A. The moral law is the declaration of the will of God to mankind, directing and binding every one to personal, perfect, and perpetual conformity and obedience thereunto, in the frame and disposition of the whole man, soul, and body, and in performance of all those duties of holiness and righteousness which he oweth to God and man: promising life upon the fulfilling, and threatening death upon the breach of it.
Section 2 of chapter 19 is also reinforcing the truth that God's moral law remained in force after the fall under Moses and for the New Testament church - yet for believers not as a covenant of works. This point was especially important for the Divines to emphasize given their concerns of antinomian influences in England at that time, which concerns hung over the Westminster Assembly deliberations. Also playing into the Divines' concern was the interpretation of some more radical groups who advocated that with the coming of Christ that obedience to the moral law as a rule of righteosness was no longer binding for believers.