I received some push-back on my negative review of Griffiths's Covenant Theology because of my belief that Old Testament saints are not New Covenant members. It is important to remember that there are nuanced opinions in many biblical topics, not only among Christians in general (which is why we have so many denominations), but also among Reformed Baptists. Based on what I read in the Bible along with other Reformed Baptist teachings and Baptist Covenant Theology books, I believe that there is a promise of the Covenant of Grace in the Old Testament which was fulfilled in the New Covenant. But I think that it's anachronistic to say that Old Testament saints are part of the New Covenant.
This weekend I listened to Reformed Pastor Jordan Hall's podcast dated 12/3/16 and titled "That Connect316 Commercial." Early in his show, he answered a listener's question on the differences between Reformed Baptist and Presbyterian Covenant Theology. I wouldn't present my view on Reformed Baptist Covenant Theology with the same terminology as Pastor Hall; however, we both agree that the New Covenant was not present in the Old Testament. In his explanation, Pastor Hall calls the New Covenant the Covenant of Grace.
From Pastor Hall's show (~27:10):
"Listener's question: How do Reformed Baptists view the Covenants differently from Presbyterians?
Pastor Hall's answer: Chapter 7 [Of God's Covenant] in the London Baptist Confession of Faith is different from the Westminster Confession of Faith. The idea that Reformed Baptists are just Presbyterians who don't baptize infants is fundamentally flawed. Reformed Baptists do not believe that Abraham was under the Covenant of Grace; that it [the Covenant of Grace] is entirely the same in substance, different in administration [this is the Presbyterian Covenant Theology view]. We [Reformed Baptists] can see types and shadows of the Covenant of Grace in the Abrahamic Covenant, the Mosaic Covenant, the Adamic Covenant, and the Noahic Covenant. Everybody who has ever been justified has been justified by faith. The Covenant of Grace did not come into time and space historically until Christ.
Reformed Baptists do not agree with the concept that it [the Covenant of Grace] is exactly the same in substance, it's just different in administration. No, we would say it's slightly different in substance; it's a different covenant. They [Old Testament saints] were not under our covenant [Covenant of Grace]. It was a different covenant. They were justified by the retroactive work of Christ upon the cross, but that doesn't mean they were under the Covenant of Grace; they were saved retroactively. They were under the Covenant of Works. We see God punishing them because they are under the Covenant of Works and they couldn't fulfill it. We see God's judgment on the house of Israel because they were very clearly under the Covenant of Works and not of Grace. The only way they were under the Covenant of Grace, even the Patriarchs of old who had faith, was in the typological foreshadows of Christ.
The Covenant of Grace itself did not come into time and space historically until Christ. So certain things are different in substance as well as in administration. The concept of being in a covenant based on who your parents are, your lineage, that's under Abraham; that's unique to the Abrahamic Covenant because God was building a nation that would foreshadow the church. That's gone now. This is a spiritual covenant. We enter this covenant by faith. So you don't give the covenant sign of baptism unless someone is of the covenant by faith. Abraham is not the head of this covenant [of grace]; that is Christ. Therefore, Reformed Baptists do not hold to infant baptism because of Covenant Theology. Reformed Baptist are not mostly Presbyterian."
"Having therefore, brethren, boldness to enter into the holiest by the blood of Jesus, By a new and living way, which he hath consecrated for us, through the veil, that is to say, his flesh; And having an high priest over the house of God; Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water. Let us hold fast the profession of our faith without wavering; (for he is faithful that promised;)," (Heb. 10:19-23).