Paul, through his use of Greek and the example of Abraham, tells us unambiguously that a right standing in the eyes of the Lord is impossible through our own good deeds, for even our best works are tainted by sin. Instead, we are declared righteous in His sight—we are justified—through faith alone. Like Abraham, we are justified by believing the promises of God, not by doing the works of the law, which is why the Apostle indicates that the words counted to him as righteousness in Genesis 15:6 are also written for us (Rom. 4:21—4:24a). Paul could not be clearer—we, as well as every believer who has lived before or after the giving of the Mosaic law, are reckoned as righteous before the Lord on account of the perfect righteousness of Christ that is imputed to us by faith alone.
Romans 4:24—25 reiterates this point, noting that the faith of those who believe in the one who raised Jesus from the dead will be counted unto righteousness. Here the Apostle gives us the explicitly Christian content of faith. We believe the same God that Abraham trusted, and we likewise have confidence that He can and will do what He has promised. Yet while God's promises to us and to Abraham are essentially the same, we see these promises fulfilled in a way the patriarch did not. We have the added confirmation of the Lord's Word in the death and resurrection of Jesus that we look back upon with clarity but which Abraham knew only in type and shadow. To believe unto justification today is to believe that God delivered Christ over "for our trespasses and raised [Him] for our justification."
We dare not miss the theological significance of this last statement. In the first place, we see that the active agent in the atonement was not only Jesus but also God the Father. God the Son willingly gave Himself over to His death for the sake of sinners, but the Father likewise gave up His only begotten Son. God was not at odds with Himself as the Son bore the divine curse against sin; Father and Son both handed over the Son to the demands of divine justice in order to effect reconciliation for God's people.
Our Creator also raised Christ "for our justification." Had Jesus remained dead, we would still be in our sins (1 Cor. 15:17). His death would have been no more significant than the death of any other person, for death has rightful claim only over sinners, and if Jesus had stayed dead, it would have indicated that He was a sinner and unable to atone for us. But because Jesus was perfectly righteous, death could not hold Him (Acts 2:24).
In his lectures on Romans, Martin Luther comments on the death and resurrection of our Savior, showing that it demonstrates that Christ’s "death not only signifies but actually effects the remission of sin as a most sufficient satisfaction." We can have confidence that our sin has been fully and finally atoned for because of the resurrection of Christ. There is nothing left to be done to pay for sin. If we trust in Jesus, we are covered by His blood forever.