Acquaintance with this covenant is of the greatest importance, for whoever errs here or denies the existence of the covenant of works will not understand the covenant of grace, and will readily err concerning the mediatorship of the Lord Jesus. Such a person will very readily deny that Christ by His active obedience has merited a right to eternal life for the elect. This is to be observed with several parties who, because they err concerning the covenant of grace, also deny the covenant of works. Conversely, whoever denies the covenant of works, must rightly be suspected to be in error concerning the covenant of grace as well.
Wilhelmus à Brakel (1635—1711), The Christian’s Reasonable Service, 1.355.
In other words one cannot grasp the good news of the “gospel” of grace without it first being framed in the context of the bad news of our sin in our inability to merit righteousness via a covenant of works. The first Adam failed as our representative to fulfill God’s covenant of works; However, the second Adam kept the covenant of works perfectly on our behalf and imputes His works to our account, and was penalized for our violating the covenant of works. We are all under the covenant of works inasmuch as we all must be perfect and Holy as He is holy. Those conditions never are lessened of lifted. We must be saved by keeping the covenant of works. So even though we are saved by works we are saved by Christ’s work of fulfilling the covenant of works on our behalf. Even though God ‘graciously’ entered into a covenant of works with Adam in the garden the requirements of that covenant was a covenant of works unlike the Covenant of Grace. In the covenant of Grace those works of the second Adam are graciously gifted to us and our sin is graciously forgiven, and the justice of God is propitiated. One cannot understand the covenant of grace apart from the covenant of works. The covenant of grace is the gracious imputation of the fulfillment of the covenant of works by Christ to the believers account. We are graciously saved by works, His works.