(Both the Catholic and Protestant traditions present the Ten Commandments with the difference being the Catholics combine into one the Protestant’s first two commandments, and the Protestants combine into one the Catholic’s last two commandments. For the Catholics, the Ninth Commandment forbids carnal concupiscence (any intense or immoral form of human desire); the Tenth forbids coveting another's goods. For the Protestants, the First Commandment forbids placing any god before Jehovah; the Second forbids making and/or worshiping idols.)

THE NINTH COMMANDMENT
You shall not covet your neighbor's house; you shall not covet your neighbor's wife, or his manservant, or his maidservant, or his ox, or his donkey, or anything that is your neighbor's (Ex 20:17).

Every one who looks at a woman lustfully has already committed adultery with her in his heart (Matt 5:28).

I. Three Kinds of Covetousness
John distinguishes three kinds of covetousness or concupiscence: lust of the flesh, lust of the eyes, and pride of life (1 Jn 2:16).

According to the etymology of (origin) "concupiscence," it can refer to any intense or excessive form of human desire, but most often it refers to desires of a sexually immoral nature. In most cases, when Bible translations use the word “lust,” they are depicting concupiscence. Christian theology generally defines “concupiscence” as the activity of the physical appetites contrary to God’s standards and human reason. The apostle Paul identifies concupiscence with the battle between the “flesh” and the “spirit” (Gal 5:16-17).

Though human desire, in itself, is not sinful, concupiscence stems from the disobedience of the first sin. It unsettles man's moral faculties and when it goes outside God’s boundaries of right and wrong, it inclines man to commit sins.

Because man is a composite being – spirit and body – and because he is under the influence of sin, there exists a certain tension in him; a certain struggle of desires and tendencies between “spirit” and “flesh.” This tension is a consequence of sin, and at the same time a confirmation of it. It is part of the daily experience of the spiritual battle going on within each of us.

However, the apostle Paul does not despise and condemn the body, which with the spiritual soul constitutes man’s nature and his ability to think and reason. Rather, Paul exhorts us to put off the morally bad desires and works of the flesh and put on the morally good desires and works of the Spirit (Eph 4:22-24). He calls us to be transformed by the renewing of our mind (Rom 12:2) and to think on the things which are above (Col 3:2; Phil 4:8). He says we are to no longer give opportunity to the devil (Eph 4:27) or our fleshly desires (Rom 13:13-14). Rather, we are to walk by the Spirit so that we will not carry out the desires of the flesh (Gal 5:16), for, as Paul writes in Galatians 5:25, “If we live by the Spirit, let us also walk by the Spirit.”

Purification of the Heart
The heart is the seat of moral desires, thinking, choices, and behavior. Jesus said: “For out of the heart come evil thoughts, murders, adulteries, fornications, thefts, false witness, slanders” (Mat 15:19). Therefore, the struggle against fleshly, ungodly covetousness includes purifying the heart and practicing temperance (self-denial, restraint, moderation). As Pastor Hermae said in relation to fleshly, ungodly covetousness and concupiscence: “Remain simple and innocent, and you will be like little children who do not know the evil that destroys man's life (Mandate 2, 1: PG 2, 916).

In the sixth beatitude, Jesus says, “Blessed are the pure in heart, for they shall see God” (Matt 5:8). In regard to the Ninth Commandment, “pure in heart” refers to those who have attuned their intellects and wills to the demands of God's holiness, chiefly in three areas: love (Rom 13:9-10; Heb 13:4; 1 Cor 7:1-9); chastity or sexual rectitude (1 Thess 4:7; Eph 4:17-19; Col 3:5; 2 Tim 2:22); love of truth and orthodoxy of faith (2 Tim 3:16-17; Tit 1:15-16; 1 Tim 1:3-4; 2 Tim 2:23-26).

The important point here is that there is a connection between purity of heart, purity of body, and purity of faith. Augustine affirmed this point when he said: “The faithful must believe the articles of the Creed so that by believing they may obey God, by obeying may live well, by living well may purify their hearts, and with pure hearts may understand what they believe” (Defide et symbolo 10, 25: PL 40, 196).

The “pure in heart” are promised that they will see God face to face and be like him (Matt 5:8; 1 Cor 13:12; Heb 12:14; 1 Jn 3:2-3). Therefore, purity of heart is the precondition of the vision of God, just as Jesus and James say that obedience to God (which equals loving God) and drawing near to God are preconditions for God loving us and drawing near to us – specifically and individually (Jn 14:21,23; Jam 4:8). And even now, purity of heart enables us to see God more nearly as He is, understand Holy Scripture more nearly as is intended, treat others more nearly as we ought (our neighbor), and regard the human body – ours and others – as a temple of the Holy Spirit.

II. The Battle for Purity
Baptism confers on the baptized the grace of purification from all prior sins. But the baptized must continue to struggle against concupiscence of the flesh and ungodly desires. With God's gracious empowerment and continued assistance, we can prevail:

Regarding this kind of prayer, Augustine gives us a model to follow: “Loving Father, I thought that self-discipline and self-denial arose from one's own powers, which I could not consistently find in myself. I was foolish enough not to know . . . that no one can be self-controlled unless You grant it. For You would surely have granted it if my inner groaning had reached Your ears and I with firm faith had cast my cares on You (Conf. 6, 11, 20: PL 32, 729-730).

Purity requires modesty – an integral part of temperance (restraint, seriousness, moderation). Modesty helps protect the inner desires and thoughts of the one practicing modesty and those observing the modest person, for modesty refuses to unveil what should remain hidden. Modesty promotes chastity, morality, and godly love. It influences how one looks at others and behaves toward them – in conformity with God’s standards for purity, love, and marriage.

Modesty protects the integrity of persons, the mystery of marriage, and the intentions of love. It encourages patience and moderation in loving relationships. It requires that God’s conditions for the definitive (sexual) giving and commitment of man and woman to one another be fulfilled (marriage). Modesty is decency. It inspires one's careful choice of clothing. It keeps silence or holds back where there is an obvious risk to purity from curiosity. It is discreet (careful not to attract attention or give offense; giving careful thought for the future).

There is a modesty of the feelings as well as of the body. It protests, for example, against the voyeuristic explorations of the human body in certain advertisements, TV programs, Internet sites, magazines or any other media that go too far in the exhibition of intimate things. Therefore, modesty avoids entertainment inclined to voyeurism and illusion. It inspires a way of life which makes it possible to resist the allurements of fashion and the pressures of prevailing ideologies that promote impurity of heart, mind, and life. Truly, purity of heart brings freedom from the widespread eroticism prevalent in our culture today.

The forms taken by modesty vary from one culture to another. Everywhere, however, modesty exists as an intuition of the spiritual dignity proper to man. It is born with the awakening consciousness of being a servant to and child of a holy God. Teaching modesty to children and adolescents means awakening in them respect for God, godliness, marriage, and a community where moral purity is promoted rather than ignored or demoted.

So called moral permissiveness rests on an erroneous conception of human freedom. The necessary precondition for the development of true freedom is to let oneself be educated in the will of God regarding purity and morality. Those in charge of education ought to give young people instruction respectful of the truth, the qualities of the heart, the sanctity of marriage, the benefits of purity, the costs of impurity, and the moral and spiritual dignity of man.

The teachings of Christ and the rest of Holy Scripture provide continual renewal for the life and culture of fallen man; they combat and remove the error and evil which flow from the ever-present attraction of sin. They never cease to purify and elevate the morality of peoples. They take the spiritual qualities and endowments of every age and nation, and with the supernatural work of the Holy Spirit, they sow seeds that when well received, will blossom, as it were, from within – where purity begins. And finally, they fortify, complete, and restore sinners to Christ and the purity of a Christ-like life.