Objection 1. It would seem that worldly fear is not always evil. Because regard for men seems to be a kind of human fear. Now some are blamed for having no regard for man, for instance, the unjust judge of whom we read (Luke 18:2) that he "feared not God, nor regarded man." Therefore it seems that worldly fear is not always evil.
Objection 2. Further, worldly fear seems to have reference to the punishments inflicted by the secular power. Now such like punishments incite us to good actions, according to Romans 13:3, "Wilt thou not be afraid of the power? Do that which is good, and thou shalt have praise from the same." Therefore worldly fear is not always evil.
Objection 3. Further, it seems that what is in us naturally, is not evil, since our natural gifts are from God. Now it is natural to man to fear detriment to his body, and loss of his worldly goods, whereby the present life is supported. Therefore it seems that worldly fear is not always evil.
On the contrary, Our Lord said (Matthew 10:28): "Fear ye not them that kill the body," thus forbidding worldly fear. Now nothing but what is evil is forbidden by God. Therefore worldly fear is evil.
I answer that, As shown above (I-II, 1, 3; I-II, 18, 1; I-II, 54, 2) moral acts and habits take their name and species from their objects. Now the proper object of the appetite's movement is the final good: so that, in consequence, every appetitive movement is both specified and named from its proper end. For if anyone were to describe covetousness as love of work because men work on account of covetousness, this description would be incorrect, since the covetous man seeks work not as end but as a means: the end that he seeks is wealth, wherefore covetousness is rightly described as the desire or the love of wealth, and this is evil. Accordingly worldly love is, properly speaking, the love whereby a man trusts in the world as his end, so that worldly love is always evil. Now fear is born of love, since man fears the loss of what he loves, as Augustine states (Qq. lxxxiii, qu. 33). Now worldly fear is that which arises from worldly love as from an evil root, for which reason worldly fear is always evil.
Reply to Objection 1. One may have regard for men in two ways. First in so far as there is in them something divine, for instance, the good of grace or of virtue, or at least of the natural image of God: and in this way those are blamed who have no regard for man. Secondly, one may have regard for men as being in opposition to God, and thus it is praiseworthy to have no regard for men, according as we read of Elias or Eliseus (Sirach 48:13): "In his days he feared not the prince."
Reply to Objection 2. When the secular power inflicts punishment in order to withdraw men from sin, it is acting as God's minister, according to Romans 13:4, "For he is God's minister, an avenger to execute wrath upon him that doth evil." To fear the secular power in this way is part, not of worldly fear, but of servile or initial fear.
Reply to Objection 3. It is natural for man to shrink from detriment to his own body and loss of worldly goods, but to forsake justice on that account is contrary to natural reason. Hence the Philosopher says (Ethic. iii, 1) that there are certain things, viz. sinful deeds, which no fear should drive us to do, since to do such things is worse than to suffer any punishment whatever.
Source: Summa Theologica (New Advent)