Hebrews 8:13 (ESV):
What is meant by obsolete?
Context: a pastor friend of mine is turning from 1689 Federalism to NCT and this Scripture is very key for him.
I always saw that the Sinaitic covenant will be obsolete at the Second Coming, and until then it is growing older in our conviction and newer in our hearts and natures as we grow in sanctification synergistically. (I also realize that I never ran my interpretation through the history of RB theology with deep roots shared by my Presbyterian brothers).
I have a meeting with him this afternoon and my theological library is at home while I am at work today.
Thank you all in advance for what I am sure will be sound exegesis and theological wisdom here.
I'll let the RB/1689 brothers answer for themselves; I'm only speaking from a Presbyterian perspective.
I'm glad the Old Covenant is obsolete and passing away. It was a yoke neither we nor our fathers could bear, though it was useful, beneficial, and performed its pedagogical and administrative work for the good of the saints for centuries while it was in effect. Now it's done, and set aside, and all for the best.
Why, then, do we covenant theologians make of the Old Testament what we do? We don't treat Sinai like our covenant-arrangement. We don't return to the pages of the OT for the ground of our doctrines and practices. However, we don't regard the OT as simply a relic, nor do we understand God's covenant-dealings with his people in the several eras of OT history as disconnected from the New Covenant era.
The OT is replete with informative redemptive history, designed so that NC people gain fuller, deeper insight into NT redemptive history and the realities of life in the present NC age. The OT is theologically rich, and not essentially different in any doctrine of our faith--creation, man, sin, redemption, justification, sanctification, eschatology, etc.; the NT doesn't have to be any longer or denser than it is, because it is the capstone of the deposit of divine revelation. The OT teaches one, universal moral standard of human behavior: thought, word, and deed; from which the NT does not deviate an inch, if anything emphasizing the absolute demand of God for moral perfection.
NCT occupies a curious space somewhere between dispensationalism and covenant theology. I think it's likely that Baptist perspectives on covenant theology (1LBC, 2LBC, 20th Cent. RB, 1689Fed, et al.) stand closest to NCT. From what I can tell, the hallmark of NCT is its assessment of the place of the moral law in connection to the NT. Sin is something intuitively recognized by Christians (or those under conviction by the Spirit); not that the NT doesn't mention specific sinful behavior, but that the NC doesn't contain law other than "the law of Christ"--somewhat nebulous and undefined.
Especially, for the NCT there is no "4th Commandment" duty of any kind in the NC, the Sabbath requirement being completely fulfilled in the Person of Christ. This appears to me as something ironic, if we juxtapose the text from Hebrews 8:13 from the OP (a "key text") with Hebrews 4:9, "There remains therefore a sabbath-resting for the people of God." If the question of NCT rests on the definition of "obsolete," I suggest the question of the abiding validity of the 4C rests on the definition of "remains."
I believe the Sinai covenant is done, obsolete, no longer in effect. The theology of Sinai remains, as does its redemptive historical significance and its moral cornerstone, the Ten Commandments. The essence of the 10C was already in the world from creation, even without the verbal containment provided in the Law given to Moses. The moral law hasn't changed, nor will it world without end. It is very useful to have so succinct and convenient a reminder for it as we have in the 10C, even for us living in the NC era. Making use of that summary does not return us under Sinai for a covenant.
The moral law was incorporate into Sinai, but was not Sinai, and is not obsolete. Believers under the NC do not swear to do all that the Lord commands as predicate to a right relationship with God. But the Lord has yet this reasonable inquiry to make of his disciples, "And why do you call me, Lord, Lord, and do not the things which I say?" Lk.6:46. "If you continue in my word, then are you truly my disciples," Jn.8:31. Genuine faith produces the fruit of obedience. When we inquire to know his moral will, the whole of Scripture explains it.
And to be clear: sanctification is by faith alone, too. It is the monergistic work (as opposed to act) of the Spirit. Man's engagement in his spiritual life doesn't make him the Spirit's "partner" for accomplishment.