In the previous post, I made an exegetical distinction between the Abrahamic Covenant and the Covenant of Grace. On one hand, a promise is given to Abraham of descendants more numerous than the stars. On the other hand, he is promised that his descendants would inherit Canaan. In light of the New Testament revelation, we are to understand these two peoples as descendants either according to the flesh of Abraham (the circumcision), or descendants according to the faith of Abraham.
This led us to conclude that there are really two covenants revealed in the Abrahamic narrative: the covenant of circumcision, often referred to as the Abrahamic Covenant, and the covenant of grace. The former was formalized with Abraham in Genesis 15 & 17 and the latter was promised yet not formalized.
At this point, we need to make a distinction between form and matter of a covenant. The form is that which is added to law or grace which results in the establishment of an actual covenant. The law by itself does not constitute the fulness of a covenant. Likewise, a promise does not constitute a covenant by itself. The law plus blessings and curses, or a promise plus faith and repentance constitutes a covenant. Now, the matter consists in those things upon which the form rests. For instance, the blessings and curses for the Mosaic Covenant were contingent upon obedience, or the keeping of the law. Therefore, the matter of the Mosaic Covenant is law. The covenant of grace was based on a promise to be unilaterally upheld by God, and thus the matter for the covenant of grace is promise, or grace, rather than law.
This is vitally important since our Reformed forerunners did not ever believe law and gospel ought to be mixed as if one was reconciled to God on the basis of one plus the other. That is a sure road to Rome. However, following Luther and Calvin, who merely followed Paul on this point, it is plain to see that one is either to be reconciled to God on the basis of obedience or on the basis of grace, yet not by both. Therefore, if one is under law, they must keep the law perfectly in order to be reconciled to God. If one is under grace, they must only receive the promise of it by faith, and it will be counted to him as righteousness.
As discussed in the previous post, the condition for the Abrahamic Covenant was circumcision. God tells Abraham, “But an uncircumcised male who is not circumcised in the flesh of his foreskin, that person shall be cut off from his people; he has broken My covenant (Gen. 17:14),” and Paul says, “And I testify again to every man who receives circumcision, that he is under obligation to keep the whole Law (Gal. 5:3).”
The matter, therefore, of the Abrahamic Covenant is law, or obedience to it. It’s form, however, is that those who are not circumcised will be cut off from their people and those who keep the covenant will receive the promised land. Since the Abrahamic Covenant is conditioned upon obedience it cannot be a covenant founded upon and completed by grace, and thus received by faith alone. The covenant of circumcision is repugnant to grace in terms of its foundation. Paul clearly states this, “For if the inheritance is based on law, it is no longer based on a promise; but God has granted it to Abraham by means of a promise (Gal. 3:18).”
This is not to say that the Abrahamic Covenant, being a covenant of works (since founded on the law), contains no grace whatsoever. Nehemiah Coxe writes:
It implies a free and sovereign act of the divine will exerted in condescending love and goodness. It is not from any necessity of nature that God enters into covenant with men but of his own good pleasure. Such a privilege and nearness to God as is included in covenant interest cannot immediately result from the relationship which they have to God as reasonable creatures, though upright and in a perfect state. For the Lord does not owe to man the good promised in any covenant he makes with him previously; but his first right in it is freely given to him by the promise of the covenant.
Thus, we do not want to deny grace in any given covenant. The question, however, is not whether or not there is grace in any given covenant, but upon what basis a covenant is established. If it be established upon requirement of obedience, it be not established upon grace. If one were to say it is established both upon obedience and faith, how does this not sound like Rome, who claims justification is a matter of faith plus works? Moreover, how is one to understand the law/grace antithesis made abundantly clear in the New Testament? If under one, a person is not under the other.
Because of this, there must be a substantive difference between the Abrahamic Covenant and the covenant of grace, one being established or contingent upon obedience, the other being contingent upon God and reception by faith, faith being supplied by God.
I have intentionally omitted language of conditionality and unconditionality, using conditionality to refer only to requirements of the Abrahamic Covenant. However, it would be helpful to note something of this distinction. The Abrahamic Covenant is obviously established upon conditionality, the conclusion thereof being reliant upon obedience in circumcision. One could say the covenant of grace also has a condition, that being faith. I am poised to accept this language with the caveat that, unlike the Abrahamic Covenant, the condition of the covenant of grace comes to us by virtue of God Himself and not by our antecedent obedience. In this sense, the covenant of grace ought to be referred to as an absolute covenant rather than a conditional covenant. This is because the covenant of grace is made and kept unilaterally (absolutely), the promise and the condition for receiving the promise (faith) being a result of the work of God, not the works of men.
Furthermore, if someone objected to this on the basis that circumcision was supplied by God, we must ask, “In what way was it supplied by God?” Because it surely wasn’t supplied through faith, since a person could circumcise without faith. If the act of circumcision is supplied by God by virtue of His common grace, which works even on believers and unbelievers alike, then that’s fine. But it also means that unbelievers, who have not faith, are simply given the common grace to obey a positive law of God.
This is no different than an unsaved man who goes to church on Sunday, yet is not regenerate. Therefore, the Abrahamic Covenant is not founded on the basis of salvific grace, but upon law. Whether or not men keep some of those laws by virtue of common grace is a rather unrelated question since, again, we are discussing the nature of covenantal requirements in themselves, not necessarily how men are enabled to fulfill those requirements. Faith is not the result of common grace but of God’s special grace administered by and through His Spirit.
Common grace is a topic better left to a different set of posts. I hope this post has led you to a clearer understanding of the substantive distinction between the Abrahamic Covenant and the covenant of grace.
 Nehemiah Coxe and John Owen, Covenant Theology: From Adam to Christ, (Palmdale: Reformed Baptist Academic Press, 2005), 36.