The Westminster Confession, bulwark of Reformed and Presbyterian churches states in chapter 7, “The first covenant made with man was a covenant of works, wherein life was promised to Adam, and in him to his posterity, upon condition of perfect and personal obedience.”
Herman Hoeksema, theological father of the Protestant Reformed Churches states in his Reformed Dogmatics, ” Adam had life but not eternal life. Nowhere do we find any proof in Scripture for the contention that God gave Adam the promise of eternal life if he should obey the particular commandment (not to eat of the forbidden tree). A command is no covenant.”
But was it not just continued blessed earthly life that would have been Adam’s had he not fallen? He was earthy (I Cor.15:47). Only since, have Christians interpreted it as ETERNAL LIFE. There was no way he could attain immortal heavenly life. Hence Goodwin, one of the Westminster delegates, and others deny the possibility of eternal (spiritual) life for Adam if he obeys, and how long would he have to obey before the reward? Scripture is silent on this hypothesis.
But Adam had friendship with God which is the essence of every divine and unconditional covenant. When he sinned he incurred separation from God which is death and would physically die in time to come. He transgressed the covenant (Hosea 8:1).
A condition, posited by followers of WCF, implies ability and any covenant of works like they posit this is, as was also the Sinaitic covenant taken on it’s own (no grace behind it) is doomed to fail because man cannot keep God’s law whether it’s “Don’t eat from that tree” or “Keep my (10) commandments and live.” In the first case because he was fallible and in the second because he is a slave to sin. Man can never merit with God as Paul points out in Romans 4:4.
Yes Adam was federal head and stands in federal headship to all humanity just as Christ does to saved humanity but I deny he failed in a covenant of works that Christ then obeyed perfectly. He transgressed a covenant of grace which would be superseded by another gracious one in which God would rekindle the friendship and put his law and Spirit in Adam’s heart that would last eternally because of Christ. THEN he possessed eternal life.