There is no place that He did this in more succinct, poignant fashion that He did in the Sermon on the Mount. We are going to go back there (to Matthew 5); and we are just going to look quickly at examples of how He magnified the law. He brought it to a much fuller understanding. (This hardly needs any explanation.)
This is a magnification by giving the law's intent. The intent of the law is to stop lawbreaking in the mind before it ever breaks out into a lust.