Day 326: Envy and Jealousy

The tenth commandment unfolds and completes the ninth, which is concerned with concupiscence of the flesh. It forbids coveting the goods of another, as the root of theft, robbery, and fraud, which the seventh commandment forbids. "Lust of the eyes" leads to the violence and injustice forbidden by the fifth commandment. Avarice, like fornication, originates in the idolatry prohibited by the first three prescriptions of the Law. The tenth commandment concerns the intentions of the heart; with the ninth, it summarizes all the precepts of the Law. CCC 2534

In today's reading, the Catechism introduces the Tenth Commandment. Envy and jealousy, or covetousness, are sins forbidden to us not only to safeguard interpersonal relations but also for the poison they do to one's heart. We can buy or trade with our neighbor things that might prove useful to ourselves, but not obsess over them or cause harm to our neighbor to obtain them. If we are in business, manipulating prices or the market for personal gain at the expense of impoverishing others is not in keeping with this commandment. Avarice is also a sin, which is essentially hoarding wealth at the expense of others. Jesus said it best, "For where your treasure is, there will your heart be also" and "You cannot serve God and mammon" (Mt 6:21, 24). 

The Catechism Compendium summarizes what is required and what is forbidden by the Tenth Commandment:

This commandment, which completes the preceding commandment, requires an interior attitude of respect for the property of others and forbids greed, unbridled covetousness for the goods of others, and envy, which is the sadness one experiences at the sight of another’s goods and the immoderate desire to acquire them for oneself. (#531)

The Catechism Companion Vol III has some good commentary on this:

Everything we do, every good and every evil, flows from the human heart. The Ninth and Tenth Commandments are all about the disorder of the human heart and about controlling our wants... We need to know when enough is enough. We must keep ourselves in check and not accumulate things endlessly... St. Augustine calls envy "the diabolical sin" (CCC 2539). As Christians, we have been adopted by God the Father as his sons and daughters. The Devil, who has rejected God, cannot have this adoption, so through envy, the Devil tries to make it so we cannot have it either. (p. 168) 

Finally, Fr. Schmitz has a great video on overcoming envy and dealing with jealousy: