Why is the Old Testament still important for us in this age of grace if the law does not save us?
The Old Testament remains important because, although the law no longer has any part in salvation or in God imputing righteousness to believers, everything enjoyed in this age of grace rests on what took place in the Old Testament. It provides the foundation, much like learning the simple part before advancing to higher mathematics.
Les explains that even though the law has nothing to do now with salvation or with God imputing righteousness to us, everything believers enjoy in this age of grace rests on what took place back in the Old Testament. He compares this to not being able to go into higher mathematics until you have learned the simple part. The righteousness of God comes through the faith of Jesus Christ unto all and upon all who believe, and people wrongly want to add something they must do. Instead, they are to believe—really believe, resting on these things with all their heart, not mere head knowledge. Paul says there is no difference: Jew and Gentile, including the Jew with all his legalism and background, stand on the same set of circumstances. The discussion then turns to imputed righteousness, going back to the first man who experienced it in Genesis chapter 3.