Much as the first three commandments set our minds squarely upon how we ought to love God supremely with all our being, the three before us in this question focus upon how we ought to love our neighbor as ourselves. These are also the three shortest commandments among the Ten, being recorded for us in Exodus 20:13-15: “You shall not murder. You shall not commit adultery. You shall not steal.”

The answer begins by noting that the Sixth Commandment requires that we do not hurt, or hate, or be hostile to our neighbor, but be patient and peaceful, pursuing even our enemies with love. We should notice that the catechism goes far beyond the simple prohibition of intentionally killing another human, whether premeditate or in a moment of rage, that is also outside of state-sanctioned executions, law enforcement, or warfare. Instead, it focuses upon how we treat our neighbor, even (or perhaps especially) our enemies. This is because Jesus Himself taught us the true depth of the Sixth Commandment, saying in Matthew 5:21-26:

You have heard that it was said to those of old, ‘You shall not murder; and whoever murders will be liable to judgment.’ But I say to you that everyone who is angry with his brother will be liable to judgment; whoever insults his brother will be liable to the council; and whoever says, ‘You fool!’ will be liable to the hell of fire. So if you are offering your gift at the altar and there remember that your brother has something against you, leave your gift there before the altar and go. First be reconciled to your brother, and then come and offer your gift. Come to terms quickly with your accuser while you are going with him to court, lest your accuser hand you over to the judge, and the judge to the guard, and you be put in prison. Truly, I say to you, you will never get out until you have paid the last penny.

Thus, we need not physically shed the blood of a fellow human to disobey the Sixth Commandment; we only need to kill with our hearts and with our mouths. With this as the standard of obedience, it would be safe to assume that we are all murderers. Harboring and speaking death upon those who bear the image of God.

The Seventh Commandment requires that we abstain from sexual immorality and live purely and faithfully, whether in marriage or single life, avoiding all actions, looks, words, thoughts, or desires, and whatever might lead to them. Again, although adultery is specifically sexual immorality with anyone who is not his or her spouse, the catechism states that this commandment requires full sexual purity from everyone, regardless of marital status. As with the Sixth Commandment, Jesus Himself gave us this understanding in Matthew 5:27-30:

You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart. If your right eye causes you to sin, tear it out and throw it away. For it is better that you lose one of your members than that your whole body be thrown into hell. And if your right hand causes you to sin, cut it off and throw it away. For it is better that you lose one of your members than that your whole body go into hell.

As with murder, Jesus makes adultery a matter of the eyes, the mind, and the heart. He states that a look of lustful intent is heart-level adultery. Interestingly, the word for lustful intent could also be translated as desired, longed for, or even coveted. Jesus used this same word to describe the Prodigal Son’s longing for the food that the pigs were eating and to describe Lazarus’ longing for the rich man’s scraps. Thus, this lust, this desire, is guttural. It is sensuous in the literal sense of the word. It is instinctual. It is an animalistic desire to satisfy one’s appetite.

This further explains why this commandment naturally follows the prohibition of murder. Just as murder is sinful because it destroys the image of God, so does adultery. Looking upon a man or woman with lustful intent necessarily means that you are seeing them as an object to be used for your own satisfaction rather than as an image-bearer of the living God to be loved and honored. Such sinful behavior, which is itself a form of idolatry, distorts who we are as well. We cannot, after all, ignore the divine insignia upon our fellow human beings without also becoming less human ourselves. A heart of lust shapes us into looking more animal than man.

And is it not Darwinian notions that have paved the way for our current sexual revolution? By classifying humans as just another animal, sex has become little more than a matter of appetite. Some people are vegetarian, while some are not. Likewise, some people are homosexual, polyamorous, pansexual, etc., while others are not. What’s the difference? If we are nothing more than genetically lucky chimps, then there isn’t one. Choosing not to marry your partner is perhaps no greater decision than choosing not to eat gluten. Without the imago Dei, adultery can be no real sin.

The Eighth Commandment requires that we do not take without permission that which belongs to someone else, nor withhold any good from someone we might benefit. The first half of this answer addresses the commandment exactly as we might think. Taking something that belongs to someone else without their permission is the very definition of stealing. Although all of creation properly belongs to God the Creator, He is gracious to give real, genuine ownership to us. Thus, as with all the commandments, it is sin because it is contrary to the nature of God. Theft is anti-God because God is the very opposite of a thief. He is a gracious giver.

The positive implications of the Eighth Commandment, of course, flow from God’s graciousness and generosity. Giving is very much the antithesis of stealing. By stealing, we wrongfully take what belongs to someone else as ours, while by giving we freely surrender what belongs to us over to someone else. The point of our work and acts of obedience is not only to fight our own sin but to also do good to our neighbors, the image-bearers around us. As God has given riches to us, we also should desire to give richly to those around us. Whenever we give joyfully and freely to others, we image God, who is free and joyful in His giving to us.