Chapter 7. Of God's Covenants
Article 1. The distance between God and the creature is so great that although reasonable creatures owe obedience unto Him as their Creator, yet they could never have any fruition of Him as their blessedness and reward, but by some voluntary condescension on God's part, which, among other ways, He has been pleased to express by way of covenants and promises.
Article 2. The provision of salvation for fallen mankind was revealed at various times and in different ways in the Old Testament, including the promise of the woman's seed, and it was most assuredly promised by God with an oath to Abraham (known also as the Abrahamic covenant), which promise expresses in substance all those same benefits of redemption and terms of salvation as are contained in the gospel of the New Covenant. There is and has been, therefore, but one way of salvation from the beginning, through both Old Testament and New Testament times.
Article 3. The Old Covenant, being that covenant instituted at Sinai through Moses, did in no way alter this promise of salvation (either by change or addition), but rather by exposing man's unrighteousness pointed to the need for God's gracious provision of redemption and salvation through His appointed Savior. Moreover, the Old Covenant was not itself redemptive, and did not provide a means of salvation, but only described the righteousness that is of the law.
Article 4. In the New Covenant God has promised the effectual conversion of the hearts of His people, whereby He writes His laws on their hearts, such that they will surely know the Lord. The New Covenant, of which Christ is the Mediator, is therefore that covenant through which we are saved, being one with the Abrahamic covenant, ratified by the blood of Christ, and promising the gift of the Spirit.