WSC Q&A #79

Q: What is the Tenth Commandment?
A: The tenth commandment is, you shall not covet your neighbor's house, you shall not covet your neighbor's wife, nor his manservant, nor his maidservant, nor his ox, nor his donkey, nor anything that is your neighbor's.
Luke 12:15 And he said to them, "Take care, and be on your guard against all covetousness, for one's life does not consist in the abundance of his possessions."

As we've seen consistently during our study of the 10 commandments, the commandments are not merely concerned with outward actions, but also the inward conditions of our hearts. If anyone has doubted that reality, then the 10th commandment should put those doubts to rest. Here we have a commandment that deals, not with external actions such as worshiping an idol, failing to keep the Sabbath, stealing, or murdering someone, but rather, here we have a commandment that deals completely with the inward condition of our hearts. Here is a commandment that deals fully with our thoughts, the lustings of our hearts, our own jealousy. Coveting is an action of the heart, and this command shows us that we are just as sinful on the inside as we are on the outside. 

Starr Meade writes:

When we know a person has murdered someone, we put that person in jail. When we know someone has stolen something, we put that person in jail as well. We all agree that murderers and thieves are lawbreakers. People often think they are law-keepers because they have never done anything that would send them to jail. They are not criminals so they must be good people. This is not how God sees it. God gave the law, "You shall not covet", for people who think they are good just because they have never gone to jail. All of us would have to admit that we have broken this law. All of us have been unhappy because we did not have something we wanted. We have felt jealous because of what someone else had or was allowed to do. God wants us to see that we all break this law. He wants us to know that even if this were the only law we had ever broken, we would be just as guilty as if we had broken every law there is.