I have read with profit Mark Jones's recent posts on the covenant of works (see here and here), having benefited from his other writings on this topic as well. Such theological clarity and historical awareness are much to be appreciated when it comes to the relationship between the covenant of works, made with Adam in the Garden, and the Mosaic Covenant, made with Israel at Sinai. Indeed, in my opinion, properly locating the Mosaic Covenant within God's unfolding covenantal economy presents the most difficult and complex challenge in covenant theology. As Anthony Burgess once observed, it is a place where many "learned men" have found themselves "like Abraham's Ram, hung in a bush of briars and brambles by the head." Given the intrinsic complexity of the issues, simplistic explanations are to be eschewed.
Though simplistic explanations of this topic are not desirable, there is a need, especially among those responsible for ministering the Word of God to the people of God on a weekly basis, to summarize complex issues in a simple, though not simplistic, way. With this in mind, I want to briefly sketch three points for thinking about the place of the Mosaic Covenant within God's unfolding plan for his people. I suggest that, taken together, these three points provide an orientation to this complex topic that is biblically, theologically, and pastorally satisfying.
(1)The Mosaic Covenant is an administration of the covenant of grace. I realize that folks on both sides of contemporary "republication" debates would affirm this point, so some qualification is in order. In saying that the Mosaic Covenant is an administration of the covenant of grace, I am affirming that the Mosaic administration, in form and structure, fits the pattern exhibited in other administrations of the covenant of grace (e.g., Abrahamic, Davidic, New covenants) and that, in form and structure, it does not follow the pattern exhibited in the covenant of works.
The covenant between Yahweh and Israel at Sinai is a covenant between redeemer and redeemed. God's gracious act of deliverance provides the redemptive foundation of the commands he issues to Israel and of the allegiance he requires from Israel (Exod 19.4; 20.2). Indeed, because the events of the exodus mark the fulfillment of God's promise, made under self-maledictory oath in Genesis 15.7-21, we should understand Israel's "pledge of allegiance" to Yahweh in Exodus 19.8 and 24.3, not as evidence that the Mosaic Covenant is a different type of covenant from the Abrahamic Covenant, but rather as evidence that the Mosaic Covenant is the realization of the Abrahamic Covenant. The one who promised to be God to Abraham and his descendants (Gen 17.7, 8) at last has brought "his people" into being (see Exod 1.7; 6.7): and as he has pledged to be their God, so they now pledge to be his people. The Sinai arrangement is not a different type of covenant from that of Abraham. It is the fulfillment and goal of the Abrahamic Covenant: the covenant relationship initiated through unilateral promise to the patriarchs is now realized in bilateral commitment between redeemer and his redeemed people.
(2) The Mosaic Covenant is a temporal administration of the covenant of grace in relation to Christ. While the Mosaic Covenant is the initial fulfillment of the Abrahamic Covenant, Israel's "I do" in relation to Yahweh her husband, it is not the final fulfillment of the Abrahamic Covenant. The Mosaic Covenant was a temporary administration of the covenant of grace, destined to be made obsolete (Heb 8.13). The Law was one of God's good gifts, but it was a gift destined for replacement by God's greater gift in and through Jesus Christ (John 1.16-17), the gift of the New Covenant. As the initial fulfillment of the Abrahamic Covenant, the Mosaic Covenant thus bears a temporary, shadowy relationship to the New Covenant, which is the final, everlasting fulfillment of the Abrahamic Covenant (Col 2.17).
(3) The Mosaic Covenant is a weak administration of the covenant of grace in relation to the flesh. The reason that the Mosaic Covenant was only a temporary administration of the covenant of grace is related to its status as a weak administration of the covenant of grace. Where does its "fault" lie (Heb 8.7-8)? Not in its structure and form, I contend (see above). The weakness of the Mosaic Covenant lies in one of its parties: the Mosaic Covenant was "weakened by the flesh" (Rom 8.3). Because the Mosaic Covenant was written on tablets of stone and not on hearts of flesh, it was ultimately only capable of exposing and condemning the treachery of God's fallen human covenant partners. It was a ministry of death leading to death (see 2 Cor 3-4).
This of course is not to ignore Old Testament teaching that the Spirit was operative under the Mosaic Covenant (Isa 63.10-11; Haggai 2.5): contrary to Dispensationalist schematizations, the contrast between the Spirit's work under the Old and New Covenants is relative, not absolute. Nevertheless, the Old Testament also teaches us that, relative to God's work in the New Covenant, God's people were largely deprived of the grace required to receive and respond to the (gracious) Mosaic Covenant in a manner that was pleasing to God (Deut 29.4; cf. 30.1-10) and therefore that they were doomed to fall under that covenant's curse from the beginning (Deut 31.27 with 21.18-23).
And indeed we must confess that God's law--in all of its covenantal forms--is destined to function this way in relation to fallen human beings: only in Christ, where the law's death-dealing sentence is realized, can the law have its proper function of instructing the redeemed, who are raised in and with Christ through the Spirit to fulfill God's law (Gal 2.19; Rom 8.4ff).
As noted above, it is only taken together that these three points may function as an effective summary of biblical teaching about the Mosaic Covenant. Denying any one of them, however, leads to serious problems.
Denying the first point, in my judgment, damages biblical preaching. If we do not see the Mosaic Covenant as an administration of the covenant of grace, then we will be tempted to read the Old Testament as one long story of Israel's failure to be the one they were never commissioned to be: the Second Adam (Rom 5.12-21). And, thus, we will fail to appreciate how Israel functions as an (to be sure, often negative) example of what it means to live in union with Christ within the covenant of grace (see 1 Cor 10.1-5; Heb 3.7-4.11), depriving ourselves of a significant dimension of Old Testament teaching (2 Tim 3.16-17).
Denying the second point amounts to Judaizing. Though few Christians would commit this mistake today, many of Paul's chief opponents in the apostolic era were those who welcomed the inclusion of Gentiles within the people of God as a sign that the latter days had dawned but who failed to appreciate the terms of Gentile inclusion because they believed that the Mosaic Covenant provided the ultimate rather than the penultimate administration for realizing the promises made to Abraham, Isaac, and Jacob. Paul's argument in Galatians 3-4 is largely concerned with refuting this error.
Denying the third point leads to legalism. Affirming the first point without affirming the third point can lead to serious theological and pastoral problems, and those of us not convinced by "republication" arguments need to acknowledge this fact. If all we do is affirm how good God's law is, how it functions as a means of gratitude for God's redeemed people, and so forth, and if we fail to acknowledge and expound the anthropological predicament of Adam's children before God's good law, then we are setting people up either for failure or self-deception in relation to the law. We must be clear: "Those who are in the flesh cannot please God" (Rom 8.8).
Moreover, we must be clear that God's solution to this predicament is not a graciously structured covenant. God's solution to this problem is the incarnation, death, and exaltation of his Son, and the outpouring of the Spirit of the risen Christ: "For God has done what the law, weakened by the flesh, could not do. By sending his own Son in the likeness of sinful flesh and for sin, he condemned sin in the flesh, in order that the righteous requirement of the law might be fulfilled in us, who walk not according to the flesh but according to the Spirit" (Rom 8.3-4). The covenant of grace--in any and every one of its administrations--is only a covenant of grace because of the mediator of the covenant of grace.
Postscript: I realize that this topic is a source of heated controversy in Reformed and Presbyterian churches today, and I count as brothers and ministers in good standing folks on both sides of the debate. Given the complexity of this issue, as well as the diversity exhibited historically across the Reformed tradition on this topic, I do hope it is an issue that can be debated with clarity and charity by those who have learned from God's law in Christ to beat their swords into plowshares and their spears into pruning hooks (Isa 2.2-4).