Guard yourself from thoughts, which appear holy and inflame an unreasonable zeal for themselves, of which the Lord speaks allegorically: 'Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves. You shall know them by their fruits' (Mt. 7:15-16). Their fruit is the languishing and breaking of the spirit. Know that everything which draws you away from humility and from inner peace and quiet, however beautiful it may seem, is nothing but false prophets who, under the cover of sheep's clothing, that is, of a hypocritical zeal to do good to their neighbors without discrimination, are in truth ravening wolves who steal you of your humility, peace and quiet, so necessary to every man who desires steady progress in spiritual life.
~ Lorenzo Scupoli (Unseen Warfare; SVS Press pg. 261)