Though rational creatures are responsible to obey God as their Creator, the distance between God and these creatures is so great that they could never have attained the reward of life except by God’s voluntary condescension. He has been pleased to express this through a covenant framework (Lk 17:10; Job 35:7-8).
Since humanity brought itself under the curse of the law by its fall, it pleased the Lord to make a covenant of grace (Ge 2:17; Gal 3:10; Ro 3:20-21). In this covenant he freely offers to sinners life and salvation through Jesus Christ. On their part he requires faith in him, that they may be saved (Ro 8:3; Jn 3:16), and promises to give his Holy Spirit to all who are ordained to eternal life, to make them willing and able to believe (Eze 36:26-27; Jn 6:44-45; Ps 110:3).
This covenant is revealed in the gospel. It was revealed first of all to Adam in the promise of salvation through the seed of the woman (Ge 3:15). After that, it was revealed step by step until the full revelation of it was completed in the New Testament (Heb 1:1). This covenant is based on the eternal covenant transaction between the Father and the Son concerning the redemption of the elect (2Ti 1:9; Tit 1:2). Only through the grace of this covenant have those saved from among the descendants of fallen Adam obtained life and blessed immortality. Humanity is now utterly incapable of being accepted by God on the same terms on which Adam was accepted in his state of innocence (Heb 11:6, 13; Ro 4:1-2; Ac 4:12; Jn 8:56).