Geerhardus Vos commented on the republication of the covenant of works in the Mosaic law:
Everyone will have to agree that for Adam, perfect keeping of the law for a fixed period of time was the means to acquire eternal beatitude that cannot be lost. When the covenant of works was broken, God could have rescinded this promise. He was no longer bound to honor it. Nevertheless, He allowed the promise and the condition to stand and repeatedly be published anew, especially by the proclamation of the Sinaitic law (Lev 18:5, “The one who does them will live by them”; cf. Rom 10:5, “For Moses describes the righteousness that is by the law,” etc.; Gal 3:12). Fulfillment of this condition from man’s side was no longer conceivable; thus the repetition must have had a different significance. This significance can only be that after the fall God gave His covenant of grace, in which the same demand and promise are fulfilled in the Mediator." (Geerhardus Vos, Reformed Dogmatics, ed. and trans. Richard B. Gaffin Jr., vol. 3 (Bellingham, WA: Lexham Press, 2012–16), 132.)
Charles Hodge wrote:
Besides this evangelical character which unquestionably belongs to the Mosaic covenant, it is presented in two other aspects in the Word of God. First, it was a national covenant with the Hebrew people. In this view the parties were God and the people of Israel; the promise was national security and prosperity; the condition was the obedience of the people as a nation to the Mosaic law; and the mediator was Moses. In this aspect it was a legal covenant. It said, “Do this and live.” Secondly, it contained, as does also the New Testament, a renewed proclamation of the original covenant of works. It is as true now as in the days of Adam, it always has been and always must be true, that rational creatures who perfectly obey the law of God are blessed in the enjoyment of his favour; and that those who sin are subject to his wrath and curse. Our Lord assured the young man who came to Him for instruction that if he kept the commandments he should live. (Charles Hodge, Systematic Theology (1872), 2.374–376.)
John Owen and Herman Witsius taught these same truths as Vos and Hodge.
I believe the Westminster delegates, like Vos, Hodge, Owen, Witsius, and others taught that there was a works principle embedded in the Mosaic Covenant. In the Westminster Confession, these delegates cited Leviticus 18:5 from the Mosaic Covenant as a proof text for the covenant of works. That's pretty amazing to me. Moses' command for Israel to "do and live" and Paul's interpretation of that command in both Romans 10:5-6 and Galatians 3:12 is the Biblical warrant for a covenant of works in Eden and a works principle in the Mosaic Covenant. God embedded a kind of covenant of works in the law of Moses, and this highlights the power, beauty, majesty, and glory of the work of Jesus Christ!
Below I list 32 ways the law functioned for the Jews under the Mosaic Covenant. The law was given to Israel as a rule of life. But there was a big problem. Namely, God said He had not given Israel a heart to do the law:
Deuteronomy 5:29: Oh, that they had such a heart in them that they would fear Me and always keep all My commandments, that it might be well with them and with their children forever!
Deuteronomy 29:4: But to this day the LORD has not given you a heart to understand or eyes to see or ears to hear.
Deuteronomy 31:26-29: Take this Book of the Law, and put it beside the ark of the covenant of the LORD your God, that it may be there as a witness against you; for I know your rebellion and your stiff neck. If today, while I am yet alive with you, you have been rebellious against the LORD, then how much more after my death? Gather to me all the elders of your tribes, and your officers, that I may speak these words in their hearing and call heaven and earth to witness against them. For I know that after my death you will become utterly corrupt, and turn aside from the way which I have commanded you; and evil will befall you in the latter days, because you will do evil in the sight of the LORD, to provoke Him to anger through the work of your hands.
Joshua 24:19: But Joshua said to the people, "You are not able to serve the LORD, for he is a holy God. He is a jealous God; he will not forgive your transgressions or your sins."
The LORD told Israel they would fail to keep the law (Deuteronomy 30-32). The fact that Israel broke covenant with God and was exiled is a great proof of a works principle in the Mosaic Covenant. This will never happen to the Church. The Church will never be exiled! The Church will triumph through the blood of the Lamb as God saves all His elect from every tribe, tongue, and nation as a pure, spotless bride. And why? Because unlike Israel, who was a little story or paradigm of the first Adam (who also failed to do and live), Jesus – the second and true Adam, the only true and worthy Israelite Who ever lived – He came and He did and lives forevermore! He alone conquered sin, death, and Satan. He alone did the law perfectly whereas all others have failed. Therefore, He lives!
And by faith we can live in Him! So the primary function of the law for all the unregenerate Jews (which was most of them for most of Israel's history!) in the Mosaic Covenant was to drive them to Christ – and oh how gracious this was! Only with the ushering in of the New Covenant is the law fully established – as Paul says (Romans 3:31). Only now in the New Covenant era do we have the fullness of the Spirit and the Law written on the hearts of God's people in a manifest way. And we have all of this because our dear Savior did and lived for us. Oh what good news this is!
Now look how the law primarily functions in Paul’s writings:
The law was . . .
1. A ministry of condemnation (2 Corinthians 3:9)
2. A ministry of death (2 Corinthians 3:7; Romans 7:10)
3. A ministry of killing (2 Corinthians 3:6; Romans 7:9)
4. Giving a knowledge of sin (Romans 3:20; 7:7)
5. Bringing about wrath (Romans 4:15)
6. Reviving sin (Romans 7:9)
7. Making sin exceedingly sinful (Romans 7:13)
8. The strength of sin (1 Corinthians 15:56)
9. Making nothing perfect (Hebrews 7:19)
10. Not taking away sins (Hebrews 10:4)
11. Weak and unprofitable (Hebrews 7:18)
12. An inferior covenant, based on inferior promises (Hebrews 8:6) (Compared to the New Covenant)
13. At fault (Hebrews 8:7-8)
14. Not the way to inheritance (Galatians 3:18)
15. Not able to give life (Galatians 3:21)
16. Confining all under sin (Galatians 3:22)
17. A yoke not able to be borne by the Jewish Fathers, Peter, and the Apostles (Acts 15:10)
18. In direct contrast to New Covenant Faith (Romans 10:5-6; Galatians 3:12)
19. Enabled the imputation of sin. It acted in a particular, specific way under the Adamic and Mosaic covenants that it did not act outside of those covenants (Romans 5:14)
20. Imprisoning sinners until faith came (Galatians 3:23)
21. A school-master to lead us to Christ (Galatians 3:24)
22. Not of faith (Galatians 3:12)
23. Promised life but brought death (Romans 7:10)
24. Was added because of transgressions (Galatians 3:19)
25. Was added to increase transgressions, and so sin abounded (Romans 5:20)
26. In its proper use, was not given for the just, but for the lawless (1 Timothy 1:8-11)
27. Contrasted with grace and faith (Romans 4:13-16; Romans 6:14)
28. Condemning Israel while the promise made to Abraham rescued them from destruction over and over again (Exodus 32:9-13; Leviticus 26:40-42; Deuteronomy 4:25-31, 9:4-5, 23-27; 2 Kings 13:1-26; and Micah 7:18-20)
29. Was broken by Israel. Therefore they were exiled for breaking covenant with God. This is in stark contrast to the New Covenant. The Church will not break the New Covenant, but will ultimately triumph through the blood of the Lamb as God gathers all His elect from every tongue, tribe, language and nation!
30. Whatever it says it says to those who are under the law that every mouth may be stopped, and the whole world may be held accountable to God (Romans 3:19)
31. Compared with the elementary principles of the world that held people under bondage (Galatians 4:1-11)
32. Held people under bondage (Galatians 4:25)
Only if we first meet the law face to face the way it is described above will we, through the law, die to the law so that we might live to God (Galatians 2:19), belong to Christ (Romans 7:4), and bear true, lasting, God-glorifying fruit for Him! Only then can we say with the Psalmist: "How sweet are your words to my taste, sweeter than honey to my mouth! . . . The law of your mouth is better to me than thousands of gold and silver pieces" (Psalm 119:72, 103).
When Paul wrote about the law, the graciousness of the sacrificial system was not his focus. He focused primarily on the “do and live” aspect of the law, just like the LORD His God:
Jeremiah 7:21-23: Thus says the LORD of hosts, the God of Israel: "Add your burnt offerings to your sacrifices, and eat the flesh. For in the day that I brought them out of the land of Egypt, I did not speak to your fathers or command them concerning burnt offerings and sacrifices. But this command I gave them: 'Obey my voice, and I will be your God, and you shall be my people. And walk in all the way that I command you, that it may be well with you.'
And over and over again, God's people broke His law (the Mosaic legislation): they did not do and live, and appeal was made to the promises made to Abraham for mercy:
Failure to “do and live” – Exodus 32:9-10: And the LORD said to Moses, "I have seen this people, and behold, it is a stiff-necked people. Now therefore let me alone, that my wrath may burn hot against them and I may consume them, in order that I may make a great nation of you."
Mercy through the Abrahamic Covenant: Exodus 32:11-14: But Moses implored the LORD his God and said, "O LORD, why does your wrath burn hot against your people, whom you have brought out of the land of Egypt with great power and with a mighty hand? Why should the Egyptians say, 'With evil intent did he bring them out, to kill them in the mountains and to consume them from the face of the earth'? Turn from your burning anger and relent from this disaster against your people. Remember Abraham, Isaac, and Israel, your servants, to whom you swore by your own self, and said to them, 'I will multiply your offspring as the stars of heaven, and all this land that I have promised I will give to your offspring, and they shall inherit it forever.'" And the LORD relented from the disaster that he had spoken of bringing on his people.
Mercy for sinners based on the Abrahamic Covenant: Leviticus 26:40-42: But if they confess their iniquity and the iniquity of their fathers in their treachery that they committed against me, and also in walking contrary to me, so that I walked contrary to them and brought them into the land of their enemies- if then their uncircumcised heart is humbled and they make amends for their iniquity, then I will remember my covenant with Jacob, and I will remember my covenant with Isaac and my covenant with Abraham, and I will remember the land.
Stephen Dempster comments on this passage: Moreover, the book [Leviticus] concludes on a negative note with a list of blessings for obedience to the covenant and curses for disobedience. The curses (Lev. 26:14-39) far outweigh the blessings (Lev. 2:3-13). The imbalance indicates an expectation of covenant violation. In addition, the last curse of exile (Lev. 26:33-39) proves to be the ultimate curse that Israel could experience. It is the death of the nation. Hope is held out for Israel in a foreign land, however, and that hope is grounded not in the Sinai covenant but in the Abrahamic covenant, which is repeated three times in one verse (Lev. 26:42). If the people confess their sins and have a change of heart, the covenant with the patriarchs will be remembered, and the end of the exile is implied. (Stephen G. Dempster, Dominion and Dynasty: A Theology of the Hebrew Bible, New Studies In Biblical Theology series, D. A. Carson (ed.), (Downers Grove: InterVarsity Press, 2003), 104.)
Mercy from the failure to obey the Mosaic Covenant through the Abrahamic Covenant: Deuteronomy 4:25-31: When you father children and children's children, and have grown old in the land, if you act corruptly by making a carved image in the form of anything, and by doing what is evil in the sight of the LORD your God, so as to provoke him to anger, I call heaven and earth to witness against you today, that you will soon utterly perish from the land that you are going over the Jordan to possess. You will not live long in it, but will be utterly destroyed. And the LORD will scatter you among the peoples, and you will be left few in number among the nations where the LORD will drive you. And there you will serve gods of wood and stone, the work of human hands, that neither see, nor hear, nor eat, nor smell. But from there you will seek the LORD your God and you will find him, if you search after him with all your heart and with all your soul. When you are in tribulation, and all these things come upon you in the latter days, you will return to the LORD your God and obey his voice. For the LORD your God is a merciful God. He will not leave you or destroy you or forget the covenant with your fathers that he swore to them.
Deuteronomy 9:5: Not because of your righteousness or the uprightness of your heart are you going in to possess their land, but because of the wickedness of these nations the LORD your God is driving them out from before you, and that he may confirm the word that the LORD swore to your fathers, to Abraham, to Isaac, and to Jacob.
Deuteronomy 9:23-27: And when the LORD sent you from Kadesh-barnea, saying, 'Go up and take possession of the land that I have given you,' then you rebelled against the commandment of the LORD your God and did not believe him or obey his voice. You have been rebellious against the LORD from the day that I knew you. "So I lay prostrate before the LORD for these forty days and forty nights, because the LORD had said he would destroy you. And I prayed to the LORD, 'O Lord GOD, destroy not your people and your heritage, whom you have redeemed through your greatness, whom you have brought out of Egypt with a mighty hand. Remember your servants, Abraham, Isaac, and Jacob. Do not regard the stubbornness of this people, or their wickedness or their sin . . .
2 Kings 13:23: But the LORD was gracious to them and had compassion on them, and he turned toward them, because of his covenant with Abraham, Isaac, and Jacob, and would not destroy them, nor has he cast them from his presence until now.
Micah 7:18-20: Who is a God like you, pardoning iniquity and passing over transgression for the remnant of his inheritance? He does not retain his anger forever, because he delights in steadfast love. He will again have compassion on us; he will tread our iniquities under foot. You will cast all our sins into the depths of the sea. You will show faithfulness to Jacob and steadfast love to Abraham, as you have sworn to our fathers from the days of old.
Paul contrasted the “do and live” of the Mosaic law with New Covenant faith. Stephen Westerholm is very helpful on this point:
The point is both obvious and crucial that what Paul means by “law” in Galatians 3:10-14 [and Galatians 3:18 as well for our purposes] does not differ from other passages we have considered: the “law” refers not to the Pentateuch, but to the divine requirements imposed upon Israel at Mount Sinai and intended (need it be said?) to be done. But whereas in other passages it was regarded as self-evident that the law was to be done or kept, that it was not to be transgressed, here the axiom is made the basis for a fundamental claim about the nature of the law: since the basic principle of the law is that it requires deeds, it “does not rest on faith.” Faith and deeds (or faith and the law) are seen – in this context at least – as exclusive alternatives. (Stephen Westerholm, Perspectives Old And New On Paul: The “Lutheran” Paul and His Critics, (Grand Rapids: Eerdmans, 2004), 304-305.)
I am indebted to Dr. Scott Clark, one of my professors at Westminster Seminary California, for most of the quotations in this post. For more information on this topic, please see: Resources On The Republication Of The Covenant Of Works