I find that discussions of this sort are quick to devolve into arguments over minutae, but especially so when we segment or attempt to demarcate the covenants too rigidly or fixedly. For example, is the Davidic covenant to be understood as a subordinate or appended clause of the Mosaic covenant? The Israelites who lived during the monarchical period were under the Mosaic economy after all, and Deuteronomy 17:14-20 specifically delineates the duties and prohibitions of the regal office. If one accepts that the monarchy is part of the Mosaic covenant, then the typology at play begins to assume a greater cohesiveness. The king, as the representative head of God's covenant people, was entrusted with upholding the burden of obedience, the nation enjoying blessing or suffering calamity largely on account of the ruler's actions. In spiritual matters especially, the Scriptures seemingly describe the character of the people as largely imitative or following after the pattern set by the king (i.e. "as the king goes, so goes the people"), something that can likewise be read typologically.
In this respect, then, the principle of works under the Old Covenant typifying the active obedience of Christ and the heavenly inheritance procured by it ought perhaps best be interpreted through the lens of OT kingship; that is, in a federal sense. It is this principle of
obedience on behalf of others that the prophets, and Isaiah most of all, reiterate and expand upon; the righteous, redeeming work of Messiah, wrought for the sake of His people and for God's glory, and freely imputed and shared with the elect. With respect to the works themselves, both of the people as well as the rulers, the purity of God's holy standard as exhibited in the Law would have at every occasion of its public reading or private remembrance convicted those persons who esteemed their works as 'congruously meritorious', and humbled them to the seek the only basis of God's being propitious towards them; namely, the free promise of grace, adoption, and inheritance that was made to Abraham and founded on the Lord Jesus Christ, exhibited to them via the Mosaic worship and whose advent was foretold by patriarchal utterances (Genesis 3:15, Genesis 22:8, Genesis 49:10, Numbers 24:17, Deuteronomy 18:15-19).
As it is faith in Christ alone that makes our works acceptable and pleasing unto God (John 6:28-29, Hebrews 11:6, 1 John 3:23), and that such works are "good" only as they are founded upon His commandments, per WCF 16.1-4, then I believe it reasonable to conclude that even under a
strict view the works of the Mosaic economy, with the respect to the
duties enjoined upon the people, the Levites, and the priesthood, are typological of the active obedience of Christ, irrespective of the nation's success in its fulfilling of the terms, for the simple reason that such duties were likewise entrusted to and fully discharged by Jesus. Christ is the true Israel, after all. And it is precisely for that purpose that the regal office was set up, so as to lead and shepherd the nation in conformity to God's Word (Deuteronomy 17:18-20, 2 Samuel 5:2) and for its occupier to "live out" the terms of obedience, albeit imperfectly, with the expectation that Messiah would complete the whole of the work (1 Chronicles 17:11-14, Psalm 89:19-37). There is good reason that Calvin describes the Old Covenant's purpose as to essentially hold the people "in suspense" (Beveridge's choice of translation) and keep alive the hope of salvation until Christ's advent (Calvin, Instit. 2.7.) It is in that regard that I see the Biblical typology of OT works as fore-shadowings of Christ's perfect ministry, a view I hold to be in good standing among the majority of Reformed theologians.
As to Venema's objections that Kline's typological views are untenable owing to the diametrically opposed principles of inheritance ostensibly present in the Mosaic covenant, that of works and that of faith, I don't really see the tension. It is certainly there if one is reading through Exodus the first time and one is impressed by the "sense" of the formal, bi-lateral nature of the covenant between Israel and YHWH, likened unto marriage bond in many later prophetic passages, as well as the sanctions pronounced against infidelity and disobedience; in sum, it has all the appearance of a conditional legal treaty. Yet the substance of the covenant is revealed when Moses descends from the mount and finds the people polluting themselves with gross idolatry; God's anger consumes the instigators of the apostasy without mercy, yet when Moses ascends the mountain to appease the Almighty what ground for pleading does he adduce? Works? Nay, but the very loving kindness of God Himself and the steadfastness of the promise made to the fathers, to be God to them and their children afterward (Exodus 32:11-13). The inheritance is manifestly rooted in the kindness of God towards His people, who manifested to us by faith and the fruit of repentance, as contrasted with the unbelieving multitude. Hence, it is not on account of their righteousness that He gifts them the land of Canaan nor its physical blessings, as He plainly states (Deuteronomy 9:5-6), but wholly to His own good pleasure and steadfast love (Deuteronomy 7:7, Isaiah 1:9, Lamentations 3:22). So likewise are all spiritual blessings in Christ. Yet this in no way obscures or glosses over the "terms and conditions" of the covenantal administrations, either old or new. As
@Semper Fidelis and
@MW have pointed to elsewhere, the distinction between antecedent and consequent conditions, and the way in which God fulfills BOTH in the course of His decree to save, is highly relevant to this discussion. The fact such heavy judgment fell upon NT Jersusalem in fulfillment of the curses and punitive sanctions issued by the LORD and his prophets is illustrative of the validity of this truth; that is, the shared substantial basis of the covenants.
I'm not as astute in the nuances of typological theology as some of our other esteemed board members, but I hope these thoughts help steer the discussion.