One of the main branch offices of Christ's mediatorial work, specifically His priestly office, is as the Testator of the covenant of grace. The covenant of grace of which Christ is the Mediator bears the name and has the nature of a will and testament. This is why our Lord when referring to the New Covenant, which is the establishment in time of the everlasting covenant of grace, sometimes called it the New Testament. He referred to His blood as the "blood of the New Testament" (Matthew 26:28). His blood is also called the "blood of the covenant" (Hebrews 10:29) and the "blood of the everlasting covenant" (Hebrews 13:20). This shows that the death of Christ as the Testator of the Covenant was the fulfillment of the terms and conditions of salvation. This is why the Gospel is the preaching of God's promise of salvation conditioned on Christ. Here we see a comparison to the last wills and testaments of men. The covenant of grace could be described as God's will and testament to His elect in Christ. This covenant is founded upon God's free, sovereign will without any influence from another.
I. CONSIDER HOW THE COVENANT IS LIKE A WILL AND TESTAMENT.
A. This covenant has articles - All of the articles of this testament are of God's own good will and pleasure. The articles of it -- Jeremiah 31:31-34 - That He will be the covenant God of His people; that they shall be His children; that they will be His heirs, and joint-heirs with Christ; that they shall enjoy all the blessings of grace, redemption, pardon, justification, regeneration, conversion, perseverance in grace, and glory. God has bequeathed to His people in this will all grace here and all glory hereafter with no conditions or stipulations upon them. It is of pure promise as all conditions and stipulations are upon Christ as the Testator of the covenant.
B. This covenant has specific heirs (Romans 8:16-17) - Christ is the main heir and His people are joint-heirs with Him. In every last will and testament, there are specific heirs chosen by the author of the will. He doesn't simply will his possessions to everybody in general if they do their part to earn them. God, the Author of this will and testament, chose a people out of Adam's fallen race and gave them to Christ. He willed that they should be heirs with Christ (Ephesians 1:3-5).
We might ask how Christ can both an heir and the Testator of the covenant. Remember, as Mediator He represents both God and men. As the Representative of the Godhead, He is the Testator of the covenant. As the Representative, Substitute, and Surety of the elect, He is an heir, and they are joint-heirs with Him. In His official subordination to the Father, the Father promised Him a mediatorial kingdom upon His fulfilling all the conditions of the salvation of the elect. In fact, whatever has been bequeathed by God in this testament is given first to Christ and then is dispensed by Him to the heirs of promise. In this sense He is also the Executor of the will as well as Testator.
C. This covenant is unalterable - Once the Testator of the will has died, the will is legally unchangeable. It cannot be altered legally. So it is with the covenant of grace. Once the immutable God purposed it and set it into action, it was unchangeable. The covenant of grace is ordered in all things and sure. It is founded upon the immutability of the divine counsel, and it is conditioned on Christ alone. Galatians 3:15 and Hebrews 6:17-18.
There are no more conditions on the heirs of this will and testament than there are on the heirs of men. The elect of God are called heirs because they are the recipients of an inheritance. For example - Romans 4:14; 8:17; Galatians 3:29; Titus 3:7; Hebrews 1:14; 6:17; 11:9; James 2:5; 1 Peter 3:7. And Galatians 3:18; Ephesians 1:11,14,18; Colossians 1:12; 3:24; Hebrews 1:4; 9:15; 1 Peter 14. So the covenant of grace is properly a covenant to Christ in which He met all the conditions, but it is a testament to His people. The legacies of this testament can be traced to the good will of God the Father and the merits of God the Son incarnate as the Testator, not to any merit in the heirs.
II. CONSIDER CHRIST AS THE TESTATOR OF THE COVENANT (Hebrews 9:13-17).
A. Hebrews 9:13-14 - This proves the value and efficacy of the Person and work of Christ to secure the eternal salvation of every sinner whom He represented, for whom He lived and died. His atonement resulted in righteousness, perfect satisfaction to God's law and justice.
How much more, then, should we expect from Christ, based upon His blood?
His blood has obtained eternal redemption for all whom He represented. This is the law of the blood which means the shedding of blood equals satisfaction to God's law and justice. Christ's blood answers all the particulars involved in our fallen condition. By His blood He merited for His people all grace here and all glory hereafter.
B. Hebrews 9:15 - The cause was to remove our guilt and defilement by the sacrifice of Himself in order to purge our consciences from dead works and free us to serve the living God! God's promise of "eternal inheritance" was conditioned on Christ as the Mediator, High Priest and Surety of all whom the Father had given Him. And for this cause this Mediator substituted Himself in their place and established a perfect righteousness "by means of death." The goal of this is an "eternal inheritance," and the means to attain this goal is the death of the Mediator! The whole inheritance of grace and glory was first committed to Christ who was appointed "Heir of all things." By Him the inheritance is communicated to the heirs of salvation, "joint heirs with Christ." These are the adopted children of God who are free to serve the true and living God!
The way God communicates the eternal inheritance is by promise (Galatians 3:18). This includes every promise God has ever made regarding eternal salvation.
How do we receive the promise and thereby receive the eternal inheritance?
By faith--to receive it is to believe it! If the eternal inheritance includes all benefits of Christ's mediation and death, there is no place left for our works to obtain or maintain an interest, or for our sins to exclude us from receiving what is freely provided and freely received. We receive the promise when we expect its accomplishment, trusting that God has actively engaged His character to fulfil this promise unto us, believing sinners!
The word "transgressions" includes all sorts of sins. The apostle mentions the sins of all the saints saved during the Mosaic Economy. He credits their redemption to the death of Christ! There is no way that those who lived and died hundreds of years before Christ's death could have been forgiven of their sins, declared righteous, and entitled to a heavenly inheritance except by imputation. The entire merit of Christ's whole work of satisfaction was charged to their account hundreds of years before it was actually accomplished. They received it by faith in Christ as typified and as preached in prophecy.
Based solely on the imputed righteousness God not only forgives all our sins but also gives us a title to an eternal inheritance. This is the great design of God in the death of His Son. By His death as Mediator Christ purchased and bequeathed to all His sheep the heavenly inheritance! God's provision of this Mediator is the greatest display of His wisdom, love, and grace. "The redemption of transgressions" is the deliverance of the transgressors from all the evils to which they were subjected. This redemption was by the full payment of a satisfactory price.
C. Hebrews 9:16-17 - To show more of the sufficiency of the blood of Christ and the certainty of the salvation of all for whom He died, the apostle follows the example of wills and testaments. A man's heirs actually possessing all his worldly goods is conditioned upon his death. As long as he lives he may give them gifts, but they cannot inherit his goods until he dies. In the same way, all of eternal salvation is conditioned upon the death of Christ. God promised His elect an eternal inheritance conditioned upon Christ satisfying law and justice in His death. Our natural deaths will ratify our wills unto our heirs. We cannot change or annul our wills after we are dead. After our deaths that will must be executed according to our directions. Christ's death has ratified His will for all His heirs whom the Father has given Him from the foundation of the world (John 6:37).
The testament is not in force while the testator lives.
Does this mean that the Old Testament saints had to wait upon the death of Christ to receive the full possession of eternal life?
No, they were blessed with eternal, spiritual life, and the whole inheritance of grace even before Christ actually came and died. They looked forward to His coming and His dying according to God's promise. They believed this promise of eternal salvation and final glory conditioned on Christ alone, and they plead His righteousness as the only ground of salvation. They had full possession of eternal life based on Christ's death because it was always sure and certain that Christ would come and die and ratify the will (2 Samuel 23:5 - "sure mercies of David"). God is faithful and wise and powerful enough to provide every means and remove every obstacle in fulfilling His promise to all the heirs. Christ has always lived and reigned as Mediator to determine the time in which all those to whom He has willed the heavenly inheritance would be recipients of it. All spiritual blessings, all grace and glory, are in His power.
In this we are reminded of the spiritual condition of multitudes who claim to believe in Christ but who deny that which honors Him--salvation conditioned on Him alone. It is sad to see the spiritual ignorance of the majority of professing Christians who know little or nothing of such a Mediator or of the Covenant of promise. Few who claim to believe in Christ have even heard of an imputed righteousness. Even fewer have received it by faith as the only ground of salvation. Today's modern heresy of salvation conditioned on faith, repentance, and perseverance blinds people's minds to the glory of God in salvation conditioned on Christ alone. This is one of the things that Satan uses to keep sinners condemned without repentance.
Sinners need to hear and understand the issues of the Gospel as set forth in "Jesus Christ, and Him crucified." This means that He fulfilled all conditions, all righteousness, and that this demands the salvation of all for whom He died. There are no legal obstacles for all the heirs of promise to obtain and keep all that Christ has earned and bequeathed to them. There are no conditions on them. You are commanded to receive Him and all that He has earned and bequeathed freely. You are commanded to expect the whole inheritance of grace based on His righteousness alone and reject all works, all deeds, performed by you as forming any part of the ground of salvation. God will save you and bless you for Christ's sake alone!