Exodus 20:15

Since charity is the end of the Law, we must seek the definition of theft from thence. This, then, is the rule of charity, that every one’s rights should be safely preserved, and that none should do to another what he would not have done to himself. It follows, therefore, that not only are those thieves who secretly steal the property of others, but those also who seek for gain from the loss of others, accumulate wealth by unlawful practices, and are more devoted to their private advantage than to equity. Thus, rapine is comprehended under the head of theft, since there is no difference between a man’s robbing his neighbor by fraud or force. But, in order that God may the better withhold His people from all fraudulent injustice, He uses the word theft, which all naturally abhor as disgraceful. For we know under how many coverings men bury their misdeeds; and not only so, but also how they convert them into praise by false pretexts. Craft and low cunning is called prudence; and he is spoken of as provident and circumspect who cleverly overreaches others, who takes in the simple, and insidiously oppresses the poor. Since, therefore, the world boasts of vices as if they were virtues, and thus all freely excuse themselves in sin, God wipes away all this gloss, when tie pronounces all unjust means of gain to be so many thefts. Nor let us be surprised that this decision should be given by the divine tribunal, when the philosophers deliver nearly the same doctrine.

We must bear in mind also, that an affirmative precept, as it is called, is connected with the prohibition; because, even if we abstain from all wrong-doing, we do not therefore satisfy God, who has laid mankind under mutual obligation to each other, that they may seek to benefit, care for, and succor their neighbors. Wherefore He undoubtedly inculcates liberality and kindness, and the other duties, whereby human society is maintained; and hence, in order that we may not be condemned as thieves by God, we must endeavor, as far as possible, that every one should safely keep what he possesses, and that our neighbor’s advantage should be promoted no less than our own.