The Lord points out on various occasions how the source of human actions is in the heart, within man, in the depths of his spirit; and this interiority must be kept pure and clean from disordered affections, resentments, and envy. Everything good originates in the heart, which later becomes reality in a person's external behavior. Within it, through grace, are consolidated a sincere piety in dealing with God, and pure love, understanding, and cordiality in relationships with one's neighbor. Purity of heart expands its capacity to love, while bourgeoisness, selfishness, and spiritual blindness are consequences of a tainted interiority. For from the heart also come evil thoughts, murder, adultery, fornication, theft, false witness, blasphemy, and so on. 1 This is why the Book of Proverbs warns: Guard your heart above all else, for from it flow the springs of life. The heart is the symbol of the innermost part of man.
The Lord tells us today in the Gospel of the Mass: "You have heard that it was said, 'You shall not commit adultery.' But I say to you that everyone who looks at a woman lustfully has committed adultery already in his heart." Jesus Christ declares in its most authentic sense the essence of the Ninth Commandment, which prohibits internal acts (thoughts, desires, imaginations) contrary to the virtue of chastity; any disordered affection, even if apparently clean and selfless, is also a transgression of this precept if it is not in accord with God's will in each person's circumstances.
To live this Commandment with delicacy—the condition of all true love—it is necessary, first of all, to relate to God, so that His love may ultimately fill our hearts. Furthermore, it is necessary to avoid the causes of internal temptations against chastity. These can occur when prudence is lacking in guarding the senses, when the imagination is not mortified and is allowed to wander in fantasies that distance one from reality and the fulfillment of duty, or in search of emotional compensation, vanity..., or stirring up memories. If, once these internal temptations are recognized, they are not promptly rejected and the means to clearly ward them off are not put in place, among which humble and trusting prayer is first and foremost, a confused inner climate persists, lacking in correspondence to grace, and the soul becomes accustomed to not being generous with the Lord. And, if it persists in remaining on that dubious threshold of consent, it is easy for the lack of interior mortification to become true internal sins against holy purity.
With such an attitude, it becomes difficult, perhaps impossible, to advance on the path of true spiritual progress. On the contrary, when the soul is determined to remain clean, with the help of grace, or promptly rectifies any oversights it may have made, even a small one, then the Holy Spirit, the sweet Guest of the soul, gives more and more graces. And in this way, joy grows stronger within it, which is one of the fruits of the Paraclete for those who prefer Him and renounce ridiculous compensations that often leave a residue of sadness and loneliness in the soul.
HCD