The distance between God and the creature is so great that, although reasonable creatures owe obedience to him as their Creator, they could never have attained the reward of life except by some voluntary condescension [stooping down] on the part of God.1 He has been pleased to express this condescension by way of a covenant.
1 Lk 17.10; Jb 35.7-8
Moreover, as man brought himself under the curse of the law by his fall, it pleased the Lord to make a covenant of grace.2 In this, he freely offers to sinners life and salvation by Jesus Christ, requiring from them faith in him in order that they may be saved,3 and promising to give his Holy Spirit to all those who are ordained to eternal life, to make them willing and able to believe.4
2 Gen 2.17; Gal 3.10; Rom 3.20-21 3 Rom 8.3; Mk 16.15-16; Jn 3.16 4 Ez 36.26-27; Jn 6.44-45; Ps 110.3
This covenant is revealed in the gospel: first of all to Adam in the promise of salvation by the seed of the woman,5 and afterwards by further steps until its full revelation was completed in the New Testament.6 Salvation rests upon the eternal covenant transaction between the Father and the Son concerning the redemption of the elect.7 It is only by the grace of this covenant that all of the posterity [descendants] of fallen Adam who ever were saved obtained life and a blessed immortality, because man is now utterly incapable of gaining acceptance with God on those terms by which Adam stood in his state of innocence.8
5 Gen 3.15 6 Heb 1.1 7 2Tim 1.9; Ti 1.2 8 Heb 11.6, 13; Rom 4.1-2, etc.; Acts 4.12; Jn 8.56