We know, according to Paul, that the law was given to point men to Christ (Galatians 3:24). The law tutored sinners toward the Savior because the law required perfection and none of us are. Only Christ fulfilled every jot and tittle (Matthew 5:17-18), the rest of us, failing at even one point have become accountable for all of it (James 2:10). The law teaches us that we have not obeyed the law and that we must believe in Christ for our righteousness.
What good, then, are the Ten Commandments for us as Christians? Historically, the Church has acknowledged a few different uses, but one of them is to show us the types of lawful behavior that God desires and that God enables believers to perform by His Spirit. God’s character didn’t change after Christ came. And Christ came to redeem and remake us to share more of God’s character.
Christ also summarized the law–epitomized in the Decalogue–in the Great Commandment and the Second like it. Love for God and love for one’s neighbor aren’t a replacement for the Ten, they represent two Tables within the Ten.
Loving God with all we are is a way to say that we will serve no idols, carve no images, not say His name in vain, and that we will take one day out of every seven to honor Him by not going about our business as usual. Loving one’s neighbor fulfills the remaining six which all function in human relationships–parents, spouses, those we’re mad at or lust for, ones we want to hurt or want what they have.
The law in Exodus 20 applies uniquely to Israel as part of the Old Testament, but we are endowed uniquely to understand it in light of Christ’s fulfillment and to obey it in His likeness by His Spirit.