What the Covenant involves
The concept of covenant involves the doctrines of God, Man, Salvation by Christ, the Church and the Last Things.
Covenant theology represents the whole compass of Scripture as being covered by two covenants, namely, the covenant of works, established with man in his original righteousness as created by God, and the one initiated by God’s love for sinners, appropriately denominated ‘the covenant of grace.’
God, as the Supreme and Sovereign Lord of all, and Maker of man, necessarily must take the initiative in whatever arrangement He is pleased to enter in with His creature. We understand, then, why Scripture consistently refers to the covenant as diatheke rather than suntheke. Though similar, the latter term emphasises the equality between the two covenant parties: this would be quite inappropriate to describe a covenant between the infinite God and finite man, who is, in his very nature, wholly dependent on his Creator, whether still viewed as righteous or as fallen.
Diatheke, then, more cogently describes the covenant relationship between God and man. In Paul, especially, the covenant is understood strongly in terms of divine operation and unconditional validity. The one divine will governs salvation history and climaxes in Christ who is both the end of the law (Romans 10:4) and the fulfilment of every promise (2 Corinthians 1:20).
The covenant arrangement redounds to God’s glory in manifesting His goodness and faithfulness, His grace and mercy. And yet it is always for man’s good. Since the Fall, God has always and necessarily dealt with man through the Mediator, Jesus Christ. In Hebrews, particularly, the diatheke, along with other legal terms, is used by way of illustration in the popular sense of “last will and testament” (9:16,17). Yet even here the new covenant of which Christ is the mediator bears the distinctive Old Testament sense. It involves redemption from the sins committed under the first covenant. The idea of a will is introduced only as a comparison to show why the death of Christ is necessary for the fulfilment of the covenant.
While the parties of the covenant of works were God and Adam, the covenant of grace has as its parties God and the last Adam, Jesus Christ. In this is seen the validity of John ‘Rabbi’ Duncan’s saying that “Theologically, there are only two men, Adam and Christ.”
The proviso or condition of this covenant is the Son’s perfect obedience even in His suffering the penalty of man’s disobedience, namely, death; and the promise is the salvation of all believers.
This is where the church comes in and partakes of the covenant. The covenant is for the elect, for their welfare, their eternal blessedness, and the greater declared glory of God. Christ merited eternal life for all believers, the life that was forfeited by Adam. For the scattered children of God to be gathered in and experientially enjoy fellowship with God and know Him as “their God,” they must come to faith in Christ.
As the whole plan of salvation is revealed in terms of a covenant (Romans 5:12-21; 1 Corinthians 15:22; John 5:30,43; 6:38-40; 17:4-12), so it must be highlighted that this acquired salvation is for all eternity. Christ “obtained for us eternal redemption.” He merited for the church her forgiveness and right standing before God (Hebrews 10:5ff.). He graciously ‘covenants’ to His people “a kingdom” (see Luke 22:29, lit.), a kingdom that shall not pass away.
The eschatological aspect brings out the wonder of God’s covenant: it is not merely for time and space, for unto the endless generations. “And this is the Father’s will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day” (John 6:39). Psalms 89:3 makes out of this a salient feature: “I have made a covenant with my chosen, I have sworn unto David my servant, thy seed will I establish for ever, and build up thy throne to all generations.”
The seed promise, frequently re-iterated through the prophets, and stated by Paul (2 Corinthians 6:16), is still prominent even in Revelation 21:3: “Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God.”