Structural unity of the divine covenants
Scripture presents a series of covenantal relationships, all mentioned earlier, instituted by the one true and living God. These various covenants, despite their diversity, organically relate to one another, but not in terms of replacing each other. The Abrahamic, Mosaic and Davidic covenants do not present themselves as self-contained entities. Instead, each successive covenant builds on the previous relationship. The unity of these three covenants is particularly seen in the historical experience of Israel (Genesis 15:18, 28:15, Exodus 2:24, 3:16-17, 6:4-8, 32:13-14, Joshua 1:3, I Chronicles 16:15-18, Psalm 105:8-12, 42-45, 106:45).
The genealogical administration of these three covenants also underscores the connection of each successive covenant with previous administrations. Robinson writes,
“When God determined to relate to a people covenantally, he made his arrangement a genealogical one. This genealogical aspect of the covenant is present in the Abrahamic, the Mosaic, and the Davidic covenants. It is manifested specifically in the reference to the “seed”-concept (cf. Gen. 15:18; Exod. 20:5, 6; Deut. 7:9; II Sam. 7:12). David’s son is not simply heir of the covenant promise made to David — he is heir also of the covenant promises made to Moses and Abraham. The genealogical promises of God’s covenants assure his participation in the blessings of the Abrahamic and the Mosaic as well as the Davidic covenant.” (The Christ of the Covenants, pg. 35)
This principle of the organic unity of the covenants established by a genealogical relationship finds rather dramatic expression in certain passages of Scripture, particularly in the renewal of the Mosaic covenant (Deuteronomy 5:2-3, 29:14). Jeremiah’s well-known prophecy clearly relates the new covenant to its Mosaic predecessor (Jeremiah 31:31-34), and he intertwines the Abrahamic covenant with the new covenant (Jeremiah 32:39-41). The prophet Ezekiel later combined allusions to the Abrahamic, Mosaic and Davidic covenants, with a single divine ordering (Ezekiel 37:24-26).
By the new covenant, all the promises of God found their consummation (II Corinthians 1:20). Christ indicated the point of formal inauguration of this new covenant at the covenant meal of the Last Supper, having taken the cup and declaring, (Luke 22:20) “This cup that is poured out for you is the new covenant in my blood.”
All of us alive in Christ today might read Israel’s early interactions and see that God actually made our covenant with Abraham and later renewed it at Sinai. Every generation of subsequent believers was present at the time of the making of the ancient covenant, by the genealogical principle. The Old Testament assures us, (Deuteronomy 7:9) “Know therefore that the LORD your God is God, the faithful God who keeps covenant and steadfast love with those who love him and keep his commandments, to a thousand generations,” and the New Testament elucidates it, (Galatians 3:15-16, 26-28) “To give a human example, brothers: even with a man-made covenant, no one annuls it or adds to it once it has been ratified. Now the promises were made to Abraham and to his offspring. It does not say, ‘And to offsprings,’ referring to many, but referring to one, ‘And to your offspring,’ who is Christ … in Christ Jesus you are all sons of God, through faith. For as many of you as were baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus. And if you are Christ’s, then you are Abraham’s offspring, heirs according to promise.”
Christ alone is the one whose death made immutable his “last will and testament.” Christ alone qualifies for the riches of the Kingdom, appoints faithful stewards of His wealth, and annuitizes an inheritance to His family line.