The writer to the Hebrews presents an apologetic defense of the supremacy of Christ throughout his epistle, seeking to demonstrate that there is nothing in the “old ways” to attract the follower of Christ. In every aspect Christ is superior to the former administration, so that there is nothing in the “old ways” to attract the believer in Him. It was also seen that the complex of terms related to “better” (mediator of a “better covenant,” “better sacrifices,” “better promises,” “better hope” and “more excellent ministry”) are found in distinctively soteriological contexts in Hebrews. The writer introduced the citation of Jeremiah within a context of contrast (8:6-7), continued it within the citation itself (“not like the covenant which I made with their fathers,” v. 9), and made the contrast explicit in his conclusion in 8:13. The text presents an apologetic argument in that unlike the old covenant, where “they did not continue in My covenant” (v. 9), the new covenant presents a perfect, full work of God including the internal renovation of the heart, salvific knowledge of God, and the forgiveness of sins. There is nothing in the text that suggests that there are different audiences envisioned in verses 10-12; those who have God’s law written on their hearts are also those who know the Lord savingly and likewise are those whose sins are remembered no more. Unlike the old covenant, in the new all know the Lord, “from the least to the greatest of them.” That we have accurately discerned the writer’s intention in seeing the new covenant soteriologically is borne out by reference to the second citation of Jeremiah 31 in Hebrews 10:16-17, for not only does the author cite the passage in support of one of the central soteriological arguments of the entire book (Heb. 10:10-14), but his interpretation of the final words regarding forgiveness of sins is clearly expressed in the same context.
Reformed Baptists have asserted that this passage is directly relevant to the commonly presented arguments of covenantal paedobaptists. Arguing from the common ground of a covenant of grace, Reformed credobaptists have asserted that if this passage teaches that the new covenant differs from the old in the matter of the extensiveness of the work of grace in the lives of the members (i.e., the new covenant is not a mixed covenant of regenerate and unregenerate, elect and non-elect), the most needed element of the paedobaptist argument regarding the continuity of the covenants and the covenant sign is disrupted at its most vital point. The “continuity” of the covenant of grace is seen in the expansion of God’s work of grace so that the new covenant in the blood of the Son encompasses all of God’s elect, the older administration’s ceremonies pointing forward to the perfection that would come in Christ. The new covenant is soteriologically extensive in scope: all who are in it receive eternal life. The giving of the covenant sign, then, must reflect the nature of the new covenant as the covenant in the blood of Christ, a covenant which fulfills, and hence a covenant that differs on the level of membership. If the new covenant is extensive in that all of those who are in it know the Lord and have forgiveness of sins in the blood of Christ, this fact must be allowed to speak directly to the question, “To whom do we give the sign of the new covenant?” While the common theme in paedobaptist writings emphasizes continuity (and other writings go to the opposite extreme seeking to create complete discontinuity) the biblical emphasis is upon fulfillment and completion. The “not like” of Heb. 8:9 points to a perfect covenantal work in the blood of the Son of God shed in behalf of His people.
Classically credobaptists have seen the elect filling the new covenant (due to its nature), and hence have recognized that the church is a mixed body, not to be seen as fully co-extensive with it. Apostasy, then, is normally viewed as apostasy from a profession of faith, not from membership in the new covenant. The visible church contains true covenant members and false: but since the new covenant is inherently soteriological in nature, and is made in the blood of Christ Himself, the membership thereof cannot apostatize anymore than Christ can lose His sheep (John 10:27-30) or fail to do the Father’s will (John 6:38-39). Apostasy then is not from the new covenant, but from false profession of faith in Christ, which can and does include membership in the external church. As we interact with the paedobaptist position, we will note that the assumed meaning of the classic apostasy passages is, we believe, allowed to overturn the presentation of the inspired writer regarding the perfection and extent of the new covenant.
—“The Newness of the New Covenant, Part II” in The Reformed Baptist Theological Review II:1, pp. 83-85. www.rbtr.org