"Abraham believed God, and it was credited to him for righteousness."
—Genesis 15:6

Solomon Stoddard, (the grandfather of Jonathan Edwards,) wrote in his book The Righteousness of Christ, the summation of the righteousness of the law:

It is sufficient for us if we have the righteousness of the law. There is no danger of our miscarrying if we have that righteousness. The security of the angels in Heaven is that they have the righteousness of the law, and it is a sufficient security for us if we have the righteousness of the law. If we have the righteousness of the law, then we are not liable to curse of the law. We are not threatened by the law; justice is not provoked with us; the condemnation of the law can take no hold upon us; the law has nothing to object against our salvation. The soul that has the righteousness of the law is out of the reach of the threatenings of the law. Where the demand of the law is answered, God has bound himself to give eternal life. Such persons are heirs to give eternal life. Such are heirs of life, according to the promise of the law. The law declared them heirs of life, Galatians 3:12, 'The man that doth them, shall live in them.'

One of the hallmarks of the Reformation was the doctrine of imputation. It is by the imputation of Christ's righteousness on the basis of faith that believers are justified in the eyes of God. Through, Christ, our sin debt is wiped clean, and we are reconciled to God the Father in love. Stoddard's remarks ultimately hearken to the doctrine of imputation.

According to the Pocket Dictionary of Theological Terms, imputation is "a transfer of benefit or harm from one individual to another. In theology imputation may be used negatively to refer to the transfer of the sin and guilt of Adam to the rest of humankind. Positively, imputation refers to the righteousness of Christ being transfered to those who believe on him for salvation."

In Romans 4:3 Paul quotes Genesis 15:6, “Abraham believed God, and it was credited to him for righteousness.” Thus the idea of “imputation” is introduced by the word “credited” from Genesis 15:6. This idea of imputation or crediting is introduced in connection with Romans 4:2 to show that Abraham was not “justified by works.” (“If Abraham was justified by works, he has something to boast about.”) So Paul is forging the link here between “justification” and “imputation.” We know, Paul says, that Abraham was not “justified” by works because Genesis 15:6 says “faith was credited to him for righteousness.” Thus we learn that when Paul thinks of the justifying work of God he thinks of the imputing or crediting work of God. How then does Paul conceive of this crediting or imputing work of God? There are clues as we consider the flow of thought through verses 4-6.
—Piper, John. Counted Righteous in Christ: Should We Abandon the Imputation of Christ's Righteousness. (Wheaton, Illinois: Crossway Books, 2002), pp. 54-55.