He drew near to man in a covenant of works demanding perfect obedience at Creation.
After sin entered the world he drew near to man in a covenant of grace promising life and salvation through Jesus Christ and requiring faith in him. All the individual covenants we see from Adam (post fall), to Noah, to Abraham, to Moses, to David, to the fulfillment with the coming of Christ are simply unfolding, advancing, and administering God’s covenant of grace.
Section 4 reminds us that the Scriptures uses the term testament to speak of God’s covenant of grace. A testament is a legal arrangement granting an inheritance to someone upon the death of another. The reason that the covenant of grace can be referred to as a testament is because it is an arrangement granting an inheritance to sinners upon the death of Christ. In the Old Testament of course the necessity of a substitutes death in order for God’s people (sinners each and every one) to receive the promised inheritance was set forth in blood sacrifices. Upon the coming of Christ and the fulfillment of his sacrifice that is no longer necessary. The covenant or testament is in his blood.
Section 5 points us the fact that God administered the covenant of grace differently before the coming of Christ than he has ever since.
The time before the coming of Christ is called “the time of the law”. It is called the time of the law not because people earned their Salvation but because the Scriptures the whole of the Old Testament is grounded on are the five books of Moses commonly called “the law”. In the time of the law the covenant of grace was administered through promises, prophecies, sacrifices, circumcision, the paschal lamb, and other types and ordinances. The Spirit worked during this time to bring the elect to faith and they received Salvation based on what Christ would do.
The time after the coming of Christ is called the time of the gospel. It is called the time of the gospel because all Old Testament Scriptures are now viewed in light of the good news that Christ has come and all New Testament Scriptures following “the gospels” instruct us as to the significance of the good news that Christ has come. The time of the gospel is lived in light of the Redeemer through whom every blessing of the covenant of grace comes having come and fulfilled his work on our behalf!
Section 6 tells us that now that Christ has come his person, work, and the blessings which flow from it which is the “substance” of the covenant is not set forth in the old ways any longer but through the preaching of the Word and the administration of the sacraments of Baptism and the Lord’s Supper. It then notes that though these ordinances are fewer and number and not quite as ornate and complex as those of old they are better. They are better because in them Christ and his benefits are held forth in more fullness, evidence, and spiritual efficacy, to all nations both Jew and Gentile.
The Old and New Testaments therefore do not essentially differ. They are both administrations of the one covenant of grace setting forth Christ and his benefits to those who believe. They only differ in mode of administration with the gospel dispensation having a greater glory and efficacy.