God's Word obviously shows that not every desire is wrong (Proverbs 4:5-9). It is no sin to desire knowledge, understanding, and wisdom. God's law is "more to be desired . . . than much fine gold" (Psalm 19:10). It is not wrong to desire a godly spouse. Learning is valuable, and desiring godly character is good. Others have good qualities that we might well desire for ourselves.
The word translated "lust" in Matthew 5:28 means "to set one's heart upon." But when the object desired is legitimately beyond the reach of the admirer, when admiration becomes a desire to get, one breaks the commandment. Desire of and by itself is not wrong, but desiring what belongs to another to such a degree that it dominates our thinking and motivates us to take other unlawful actions to possess the object is sin. Such covetousness often suppresses the far more important things of God—and may even cause one to forget them altogether.
When desire builds to the breaking point, people will lie, steal, commit adultery, dishonor parents, and even murder to have what they lust after. We might also break the Sabbath and destroy our witness for God by serving our desires. Truly, Paul was correct in Colossians 3:5: "Therefore put to death your members which are on the earth: fornication, uncleanness, passion, evil desire, and covetousness, which is idolatry." Breaking the tenth commandment brings us full circle through the commandments and back to the first.
There is nothing wrong, however, in merely wanting something. It is only wrong to want something so badly that we would break every law to get it, be sick with unhappiness without it, or so occupied with it that we push God out of our lives. To desire a better life does not break the command; to enter the race to keep up with the Joneses does. To want our children to have it better than we did is natural; it becomes evil only when its purpose distorts the child's values.
To love pretty things is normal. God loves beauty and has created it. We can appreciate beautiful things, but to desire them to show them off and arouse envy in others is evil. It is not wrong to desire the needs of life and even its luxuries, but a feverish passion for more—and the action it incites—breaches God's law.