TREATISE ON FORTITUDE AND TEMPERANCE · Question 1672

1Reply to Objection 3: One may watch other people's actions or inquire into them, with a good intent, either for one's own good---that is in order to be encouraged to better deeds by the deeds of our neighbor---or for our neighbor's good---that is in order to correct him, if he do anything wrong, according to the rule of charity and the duty of one's position. This is praiseworthy, according to Heb. 10:24, "Consider one another to provoke unto charity and to good works." But to observe our neighbor's faults with the intention of looking down upon them, or of detracting them, or even with no further purpose than that of disturbing them, is sinful: hence it is written ( Prov. 24:15 ), "Lie not in wait, nor seek after wickedness in the house of the just, nor spoil his rest."