To steal means to take or keep unjustly what belongs to another.  The seventh Commandment obliges us to respect the property of our neighbor.  By property we mean those things which belong to a person.
We injure our neighbor in his property:
       1) By stealing (theft, robbery)
       2) By cheating
       3) By not restoring things found to the owner
       4) By not paying our debts
       5) By damaging our neighbor’s goods.

It is a sin for children to steal from their parents, brothers, or sisters.  It is a sin to tell others to steal or to help them in stealing.  When we have injured our neighbor in his property by stealing or in any other way, we are bound in conscience to make restitution; that is, make good the damage we have done.  “I have been young, and now am old; and I have not seen the just forsaken.”

(Ps. 36:25).
 

The eighth Commandment of God is: Thou shalt not bear false witness against thy neighbor.

We commit sin against the eighth Commandment:
        1)  When we tell a lie
        2)  When we injure our neighbor’s good name.

By a Lie we mean saying what is not true, with the intention of deceiving our neighbor.  “Lying lips are an abomination to the Lord.” (Prov. 12:22).

We injure our neighbor’s good name by Slander and Detraction. Slander is falsely accusing our neighbor of something evil.  Detraction is telling the hidden faults of our neighbor without necessity.

We sin in thought against our neighbor’s good name by False Suspicion and Rash Judgment.
 False Suspicion is surmising evil of our neighbor without good reasons. 
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Rash Judgment is believing evil of our neighbor without good reasons.  “Judge not, and you shall not be judged.” (Luke 6:37). 
Whenever we have injured the good name of our neighbor we are bound in conscience to repair the injury.
“And the chief priests accused Him of many things.” (Mark 15:3).
 

The ninth Commandment of God is: Thou shalt not covet thy neighbor’s wife.

The ninth Commandment forbids impure thoughts and desires, especially in regard to married persons.  “Evil thoughts are an abomination to the Lord.” (Prov. 15:26).

Impure thoughts and desires are not sinful if we try to banish them from our mind.  When we are tempted with impure thoughts and desires we should especially pray to God, the Blessed Virgin Mary, and our Guardian Angel.  We should remember that God knows our most secret thoughts and desires. 
 Impure thoughts lead to impure deeds.
Jesus saved the woman caught in adultery from the scribes and Pharisees, who sought to stone her.  He said to her: “Go, and now sin no more.” (John 8:3-11).
“Blessed are the clean of heart: for they shall see God.” (Matt. 5:8).
 

The tenth Commandment of God is: Thou shalt not covet thy neighbor’s goods.

To covet means “to desire.”  The tenth Commandment forbids us to desire our neighbor’s goods. 
Before God the intention to steal from our neighbor is just as wicked as the deed itself.

The tenth Commandment also forbids the sins of envy and discontent.  By Envy we mean begrudging our neighbor his good fortune and success.  By Discontent we mean complaining that our lot in life is worse than that of our neighbor.
“Seek ye first the Kingdom of God and His Justice, and all these things shall be added unto you.” (Luke 12:31).
“For the desire of money is the root of all evils; which some coveting have erred from the faith, and have entangled themselves in many sorrows.” (1 Tim. 6:10).

The treasures of the Temple were coveted by Seleucus, king of Asia.  He ordered Heliodorus, the general of his army, to seize them.  When the general arrived at the Temple a mysterious horse and rider struck him down, while two Angels of the Lord beat him unceasingly. (2 Mach. 3).