To preface my question, I can't say I'm much of an OT scholar, so I may be missing a large portion of the picture. What I find confusing is that God would institute a law that would require capital punishment for certain crimes (kidnapping, sexual sins, blasphemy, hitting a parent). Now, I'm not hung up on this because I think it displays a lack of mercy on the part of the Lord-- consequences follow our actions. What trips me up about this is that if we believe that this life is a probationary period for us to work out our repentance, how would the practice of stoning someone to death for sin support that concept?
I used to understand Jesus' "go thy way and sin no more" interaction to be a rejection of that practice in the Law of Moses and a teaching about mercy. However, I've read some sources that compellingly argue that it is less of a story of mercy, and more a story showing Christ's ability to discern those who were trying to entrap Him. That because they only brought the woman and not the man, as required by the Law of Moses, and because under Roman rule, the Jews were allowed to govern themselves in some matters only (not capital punishment). Therefore, He wasn't rejecting the practice of stoning (as He had been the one to give the Law in OT times) but saying "if you're going to do it, do it by the book".
So, I guess I just fail to see how such a law supports the ultimate goal of providing salvation through repentance in this life and relying on His grace.