On the Tenth Commandment.
The Longer Catechism of the Orthodox, Catholic, Eastern Church · St. Philaret of Moscow
602. What is forbidden by the tenth commandment? All wishes inconsistent with charity to our neighbor, and thoughts which are inseparable from such wishes.
Q. 602
603. Why are we forbidden not only evil deeds, but also evil wishes and thoughts? First, because when the soul entertains any evil wishes or thoughts, it is already impure in God's sight, and unworthy of him; as Solomon says: The unjust thought is an abomination to the Lord. Prov. xv. 26 . And therefore we must needs cleanse ourselves also from these inward impurities also, as the Apostle teaches: Let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of the Lord. 2 Cor. vii. 1 . Secondly, because, to prevent sinful acts, it is necessary to crush sinful wishes and thoughts, from which, as from seeds, such actions spring; as it is said: For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies. Matt. xv. 19 . Every man is tempted, when he is drawn away of his own lust, and enticed. Then, when lust hath conceived, it bringeth forth sin; and sin, when it is finished, bringeth forth death. James i. 14, 15 .
Q. 603
604. When we are forbidden to desire any thing of our neighbor's, what passion is thereby Envy.
Q. 604
605. What is forbidden by the words, Thou shalt not covet thy neighbor's wife? All lustful thoughts and wishes, or inward adultery.
Q. 605
606. What is forbidden by the words, Thou shalt not covet thy neighbor's house, nor his land, nor his man-servant, nor his maid-servant, nor his ox, nor his ass, nor any of his cattle, nor any thing that is his? All thoughts of avarice and ambition.
Q. 606
607. What positive duties, corresponding to these prohibitions, are prescribed by the tenth commandment? First, to keep purity of heart; and, secondly, to be content with our lot.
Q. 607