d. Unfortunately, Adam disobeyed resulting in sin and death (Gen. 3; Rom. 3:23; 6:23). However, our Triune God did not leave us to ourselves. Instead, God the Father chose to redeem His people by sovereign grace by the provision of God the Son, who by His incarnation, life, death, and resurrection, secured our eternal salvation. As the incarnate Son, Jesus - the last Adam - perfectly obeyed for us as our covenant head (Rom. 5:12-21; Phil. 2:6-11; Heb. 5:1-10). As the divine Son, he bore the penalty of our sin and satisfied God’s own righteous demand against us (Rom. 3:21-26). By our covenantal faith-union in Christ, wrought by the regenerating work of God the Spirit, we stand justified before God as His redeemed, reconciled, and adopted sons (Rom. 8; Eph. 2:1-10). As new creations in Christ (2 Cor. 5:17), we are restored to the purpose of our creation: namely, to know, love, serve, and glorify God, now and forevermore, in a new heaven and new earth (Rev. 21-22).
e. The justification of God’s people has always been by grace through faith in Christ alone (Gen. 15:6; Rom. 4). There is only one way of salvation and one Meditator: namely, our Lord Jesus Christ (1 Tim. 2:5-6). Yet, the knowledge and identity of Christ Jesus, our Redeemer and covenant head, has been progressively revealed over time through the biblical covenants. God’s initial promise of a coming Redeemer is first given in Genesis 3:15. Those who believe God’s promise of a coming Savior are justified by grace through faith. As each covenant is established, in a variety of ways, God’s promise of who will redeem us and how he will do so is revealed, predicted, and foreshadowed in a more detailed way, which will ultimately culminate in the establishment of a New Covenant (Jer. 31:31-34). Through the covenants, we discover that the coming Redeemer will be Abraham’s true Seed (Gal. 3:16), a greater prophet than Moses (Deut. 18:15-18; Heb. 3:1-6), the true and obedient Israel (Matt. 2:15; John 15:1-8), our great prophet, priest, and David’s greater Son (Matt. 1:1; Acts 2:3236; Rom. 1:3-4; Heb. 1 [cf. Ps 2, 45, 110]). He will be the Suffering Servant (Isa. 53), who as our King-Priest (Ps. 110), will offer Himself as our penal substitute. OT saints believed God’s promises centered in the coming of Christ. They related to their Creator and covenant Lord under their respective covenants, yet all the covenants pointed forward to the coming of Christ and the New Covenant.
f. In fact, in and through the OT covenants, God re-establishes humanity’s lost rule in Adam by the establishment of His kingdom and saving reign (Heb. 2:5-18). In embryonic form, the OT covenants restore what was lost in the fall, yet always pointed forward to the coming of the Redeemer/Messiah who alone establishes God’s kingdom and the new creation by His life, death, resurrection, ascension, and Pentecost by the ratification of a new covenant (Luke 22:20; 2 Cor. 3; Heb. 8-10).