The prophet Isaiah knew that the true and living God is a covenant-making and covenant-keeping God. He writes of a “covenant of peace” (Isa. 54:10) and an “everlasting covenant” (55:3) between God and His people. This covenant is clearly meant to be a blessing and encouragement to the people of God. But what is a covenant?
One brief definition of a covenant is “a structured relationship.” God establishes and structures the fellowship that He has with us. Thus, the covenant is like a treaty that specifies the benefits and duties that bind the two parties together.
Most Reformed theologians understand the Bible as teaching that the first covenant God initiated was with Adam in the garden of Eden. God structured His relationship with Adam in terms of duties and benefits. The Westminster Confession summarizes the teaching about God’s relationship with Adam: “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” (7.1). But Adam, and with him all of mankind, fell into sin and disobedience, and therefore deserved the sentence of death.
But God in mercy established a different covenant for sinners, which usually is called the covenant of grace. The Westminster Confession summarizes this gracious covenant as one “whereby He freely offereth unto sinners life and salvation by Jesus Christ; requiring of them faith in Him, that they may be saved; and promising to give unto all those that are ordained unto eternal life His Holy Spirit, to make them willing, and able to believe” (7.3). The covenant of grace is presented as the blessing of life and salvation linked to the duty of faith, but even faith is a blessing that is given.
This covenant of grace was announced to Adam and Eve (Gen. 3:15) and is at the root of all other covenants in the Bible, including God’s covenants with Abraham, Moses, and David. They all come to fruition in the coming of Jesus and the great redemptive work that He did to save sinners.
Fulfillment of the previous covenants is actually the kernel of the gospel. Jesus is the second Adam, the head of a new covenant community and a new humanity. He fulfills the condition of perfect, personal obedience. By His death, He bears the wrath of God, so that in Him sinners might be forgiven and enlivened. All that Jesus did, He did to establish the covenant of grace between God and mankind.
In His covenant, the Lord assures His people of His unfailing care, which is more certain even than the mountains and the hills (Isa. 54:10). The earth itself will disappear before the mercy of the Lord will depart from His own regenerate people.
Sinners have an everlasting covenant because of the work of Christ. Because we have an everlasting and unchanging covenant, we have an everlasting inheritance. How rich is the covenant mercy of God to us.