"And he believed in the LORD; and he counted it to him for righteousness." (Genesis 15:6)
It may come as a surprise to some that both Old and New Testament believers are justified only by faith. In fact, four New Testament epistles base their arguments on justification by faith on two Old Testament passages, each quoted three times, but with each one emphasizing a different aspect.
In our text, we see that Abraham was declared righteous because of his faith (i.e., belief, same word). This verse is quoted in Romans 4:3 in the midst of a formal argument on the just nature of God and the fact that we are "justified freely by his grace through the redemption that is in Christ Jesus" (Romans 3:24). Here the emphasis is on counted. In Galatians 3:6, the word believed is emphasized, couched in the book dedicated to contrasting works and faith. "They which be of faith are blessed with faithful Abraham" (Galatians 3:9). The book of James was written to encourage believers to good works as evidence of their faith, and our text, quoted in James 2:23, emphasizes righteousness. "Faith without works is dead" (James 2:26).
The other Old Testament passage dealing with faith, which is also quoted three times in the New Testament, reads, "The just shall live by his faith" (Habakkuk 2:4). When used in Romans 1:17 just prior to the description of the evil lifestyles of the wicked (vv. 18-32), the emphasis seems to be on the word just. In Galatians 3:11, as noted above, the word faith is stressed. But in Hebrews 10:38 the author teaches that those who have been declared righteous by God live eternally by faith and will be able to cope with persecution (vv. 34-37).
Thus, the Old Testament doctrine that we are saved by faith in the work of God to solve our sin problem applies to every area of our lives and being, including our past sin, our present holy life and work, and our future eternal life. JDM