Hey Van
I think that goes back to the OT, called the Law, and the NT, called, and sometimes assumed into the word "faith". Yet another way of understanding the term 'faith'. The righteousness that comes from faith means the NT faith, as opposed to the Law. We see the Law contrasted with faith all the time. In that sense, the term faith represents the NT, or the Gospel in context, while at the same time meaning faith in the traditional way. That's the way I see it. In my mind, the righteousness by faith simply means that, Jesus' righteousness, revealed through the Gospel, comes by faith in Jesus. It's a NT reality that was waited upon before the promise could be given.
Here's a few passages that apply.
Galatians 3:18-29For if the inheritance is of the law, it is no longer of promise; but God gave it to Abraham by promise. What purpose then does the law serve? It was added because of transgressions, till the Seed should come to whom the promise was made; and it was appointed through angels by the hand of a mediator. Now a mediator does not mediate for one only, but God is one. Is the law then against the promises of God? Certainly not! For if there had been a law given which could have given life, truly righteousness would have been by the law. But the Scripture has confined all under sin, that the promise by faith in Jesus Christ might be given to those who believe. But before faith came, we were kept under guard by the law, kept for the faith which would afterward be revealed. Therefore the law was our tutor to bring us to Christ, that we might be justified by faith. But after faith has come, we are no longer under a tutor. For you are all sons of God through faith in Christ Jesus. For as many of you as were baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female; for you are all one in Christ Jesus. And if you are Christ's, then you are Abraham's seed, and heirs according to the promise.
Compare to Hebrews 11:13 These all died in faith, not having received the promises, but having seen them afar off were assured of them, embraced them and confessed that they were strangers and pilgrims on the earth.
Apart from the earthly promises, the types, there was also spiritual promises. Those which the types pointed towards. These promises began to be fulfilled with the death, resurrection, and ascension of Jesus, and the giving of the Holy Spirit's indwelling at Pentecost. Understanding that "faith" in that Romans passage implies the Gospel in it's context, we then can know that the righteousness by faith means righteousness by faith in Jesus, the Gospel. Nobody was ever saved by the Law, not even Abraham. His faith was credited as righteousness in future promises, that being Jesus, as opposed to the Law. In other words, Abraham was saved just like we are, from what Jesus did, the only difference was that He had to wait for the promises, and the Gospel He trusted in was not completely revealed in his time. It was an OT understanding of it. Isaac, picturing Jesus. Abraham, trusting that God would raise Him from the dead, just as Jesus was raised from the dead. That all pictured the cross. Abraham, trusted in types, and a promise of a future Messiah, a deliverer, thus, a righteousness by faith, just like us, but we trust in the revealed Gospel.
god crediting a persons faith as righteousness, is simply God crediting them with the righteousness of God, what Jesus did. Now credit could have a bigger context in the OT because there was not yet a righteousness of God yet established to credit them. It was credited based on the future promises of God. The Same promises that we look back of today. Today, we are credited with something that has already happened. They, OT believers, were credited with something still future. think about that in this the context of defining what this next passage is saying.
Romans 3:25-26 whom God set forth as a propitiation by His blood, through faith, to demonstrate His righteousness, because in His forbearance God had passed over the sins that were previously committed, to demonstrate at the present time His righteousness, that He might be just and the justifier of the one who has faith in Jesus.
Dave