Without the gospel, we may obey the law, but we will learn to hate it. We will use it, but we will not truly love it. Only if we obey the law because we are saved, rather than to be saved, will we do so ‘for God’ (Galatians 2:19). Once we understand salvation-by-promise, we do not obey God any longer for our sake, by using the law-salvation-system to get things from God. Rather, we now obey God for His sake, using the law’s content to please and delight our Father.
– Tim Keller