God used human authors to write the sixty-six books of the Bible over a long period of time. Thus, the books of the Bible actually form one book, with one triune Author, and one unified message of salvation. The Bible is one book because God the Holy Spirit is its Author (2 Sam. 23:2; Neh. 9:30; Heb. 3:7). The Father revealed Himself over the centuries to His people by His Word and Spirit (Isa. 59:20–21; 1 Peter 1:11; Heb. 1:1–3; 3:7). Christ is the main theme of Scripture (Luke 24:25–27; John 5:39; Acts 17:3). The covenant of grace, which spans both the Old and New Testaments, is the primary way that God reveals Christ and salvation in Him. Though this covenant is administered differently under the Old and New Testaments, Christ and the covenant of grace constitute a unified message of salvation, from Genesis through Revelation.
Westminster Larger Catechism 32–35 teaches us that we partake of the covenant of grace in Christ alone. This was true in the Old Testament, which describes the old covenant, and it remains so in the New Testament, which describes the new covenant. Though the administrations of the covenant differ between the testaments, the saints have always been saved by Christ and covenant.
How Does the Covenant of Grace Manifest God’s Grace?
The grace of God is manifested in the second covenant, in that he freely provideth and offereth to sinners a Mediator, and life and salvation by him; and requiring faith as the condition to interest them in him, promiseth and giveth his Spirit to all his elect, to work in them that faith, with all other saving graces; and to enable them unto all holy obedience, as the evidence and truth of their faith and thankfulness to God, and as the way which he has appointed them to salvation. (WLC 32)
The covenant of grace gives us everything necessary for life and salvation because it gives us Christ the Savior. The Westminster Larger Catechism directs us to the Mediator and to faith in Him and obedience to Him. He alone is the Savior and Mediator between God and man (Isa. 43:11; 1 Tim. 2:5). God offers Him to sinners indiscriminately (John 3:16). He calls the ends of the earth to look to Him and be saved (Isa. 45:22). While the Spirit must change the hearts of the elect, Jesus calls people to come to Him not because they are elect but because they are weary and heavy laden (Matt. 11:28–30). He gives life and salvation to all who come to Him. He says, “All that the Father gives me will come to me, and whoever comes to me I will never cast out” (John 6:37), upholding both divine election and the free offer of the gospel. While election should comfort us that we belong to God, we invite sinners to receive Christ because they are sinners, not because they are elect. We must not restrict the outward call of the gospel—our exhortation for people to know and believe in Jesus—more than God does, so we must preach Christ to all sinners.
God requires faith in Christ as the condition of receiving Christ and His benefits. However, benefiting from the covenant of grace requires men and women to place their faith in Christ (John 1:12). This is where election comes into the picture again, since God gives the Holy Spirit to work in the elect only the faith He demands (Isa. 59:21; John 14:16–20; Acts 16:14; Eph. 2:8–9). The Spirit also works “all other saving graces” in us, creating us in Christ Jesus for good works (Eph. 2:10). He enables us to work out our salvation “with fear and trembling” as He works in us to will and to do for His good pleasure (Phil. 2:12–13).
These “other saving graces” enable us “to all holy obedience.” While God does not save us by our good works, He saves us to be zealous for good works (Titus 2:14). Good works are the evidence of true faith and of thankfulness to God. Those who “profess to know God, but in works deny him” (Titus 1:16) do not have true faith in Christ. Good works are not the ground of our salvation, but they are the necessary fruit of our salvation. Good works are not the means of our salvation, but they are the way by which we demonstrate that we have been saved. In its broadest sense, salvation does not mean forgiveness only but means also our full transformation and reception into God’s gracious presence in glory. God predestined us to be like His Son (Rom. 8:29) and He makes us like His Son first by declaring us righteous in Christ through faith alone and then by changing us so that we, also by faith and by grace, do good works as we are brought into conformity to Jesus.
How Is the Covenant Administered Differently under the Old and New Testaments?
The covenant of grace was not always administered after the same manner, but the administrations of it under the Old Testament were different from those under the New. (WLC 33)
God administers the same covenant of grace, with Christ as the object of faith, in both the Old and New Testaments, but the outward administration of the one covenant differs between the testaments. As we have seen in previous pots, God promised that the woman’s Seed would crush the serpent’s head so that He might save His seed (His elect people) and distinguish them from Satan’s seed. In Abraham’s seed, God said in the Old Testament, all the nations of the earth would be blessed. God redeemed His seed out of the land of Egypt, from the house of bondage, and gave them the land, the tabernacle, the priesthood, and the sacrifices as pledges of eternal life, of God’s presence, and of atonement and forgiveness. David ushered in a legacy of promises, in which a son would sit on his throne forever, bringing salvation both to Israel and to the nations (2 Sam. 7; Ps. 2; 72; 89; 110; 132; Ezek. 34). Jesus was of the seed of David “according to the flesh,” but He “was declared to be the Son of God in power, according to the Spirit of holiness, by his resurrection from the dead” (Rom. 1:3–4). He is the Seed of the woman who redeems the seed of the woman—God’s people (Gal. 3:15–29).