The Tenth commandment strikes at the very root of all sins, prohibiting the selfish desire, from which springs the sinful act. He who in obedience to God's law refrains from indulging even a sinful desire for that which belongs to another will not be guilty of an act of wrong toward his fellow creatures.
Such were the sacred precepts of the Decalogue, spoken amid thunder and flame, and with a wonderful display of the power and majesty of the great Lawgiver. God accompanied the proclamation of His law with exhibitions of His power and glory, that His people might never forget the scene, and that they might be impressed with profound veneration for the Author of the law, the Creator of heaven and earth. He would also show to all men the sacredness, the importance, and the permanence of His law.
The people of Israel were overwhelmed with terror. The awful power of God's utterances seemed more than their trembling hearts could bear. For as God's great rule of right was presented before them, they realized as never before the offensive character of sin, and their own guilt in the sight of a holy God. (Patriarchs and Prophets, 309)
Reflection: To covet is to desire. It is not an outward act, but may lead to one. This makes covetousness a state of mind, a condition of the heart.