“Now to him that worketh is the reward not reckoned of grace, but of debt. But to him that worketh not, but believeth on Him that justifieth the ungodly, his faith is counted for righteousness” (Rom. 4:4,5).
As we look back at all the Old Testament types: the physical types, the narratives, the sacrifices, we exclaim: “The cross was not an accident, nor an afterthought on God’s part: He had it in mind all the while.” Surely Paul was right when he said of believers that “[God] hath saved us and called us with an holy calling, not according to our works, but according to His own purpose and grace, which was given us in Christ Jesus before the world began” (II Tim. 1:9).
It is on the basis of the cross, typified all through the Old Testament, that God now saves us by grace through faith alone, and the types show that this was indeed His eternal purpose. Furthermore salvation should be by grace through faith.
As our text, above, declares: if man could earn his salvation it would be the payment of a debt, not the bestowal of a gift — and God will never be indebted to anyone. He will never be in a position where He owes us, sinners, a debt. Nor will He ever allow us to disgrace ourselves and annoy others by our boasting about how we earned eternal life. But He can, on the basis of the penalty paid at Calvary, bestow salvation as a free gift. This is why we read:
“The wages of sin is death, but the gift of God is eternal life, through Jesus Christ, our Lord” (Rom. 6:23).
“It is the gift of God, not of works, lest any man should boast” (Eph. 2:8,9).
God owed Abraham nothing, but seeing his faith He said, in effect: “This man believes Me; I will count his faith for righteousness” (Gen. 15:6). And this He still does for those who trust Him, only He has now revealed the basis for this action: Christ’s payment for sins at Calvary. This is why, in Romans 4:5, He forbids works for salvation and declares that the believer’s faith is “counted for righteousness.” source