Why couldn't the law be set aside before Jesus died?
The law could not be set aside before Jesus died because Israel was not yet in the place where the law could be removed. That could not happen until His death. The cross is where the law was finally crucified, and until then the nation remained under the law.
Les explains that Jesus never told the Jews of His day to forget keeping the law or that they were under grace. He could not say that, because Israel was not yet in the place where the law could be set away. That could not happen until He died. The cross is where the law was finally crucified. At the time of Christ's birth, Israel was still under the law and could see nothing but their own self-righteousness. They bragged about being law-keepers, and the Pharisees especially boasted of how impeccably they had kept the law. Christ came under that same law.