What was the purpose of the Law if not to bring salvation?

The purpose of the Law was to reveal sin. For example, if you drove down a highway that had no posted speed limit, you could go as fast as you wanted to go. But if you were driving down a highway with a posted speed limit, you would be found guilty of breaking the law if you exceeded that limit. God brought up His people, teaching them to obey His commands expressed in His laws. This was necessary so that God would have contact with man through faith. If man believed God and obeyed His law, then a contact was established: faith through obedience. Subsequently, God could give more instructions and details about His intention for His people and fallen mankind.