Saint Nikolai Velimirovič
Conceal your spiritual treasures and do not reveal them unnecessarily. Behold, how men conceal and hide their material wealth and how, when forced to reveal how much they have, they always conceal the greater amount and only reveal the lesser amount. Very few are the number of men who want to reveal all that they possess, and fewer still are those who would reveal more than they, in reality, possess. This, the world considers frivolous and mindless. This clearly shows you how you need to conceal your spiritual wealth, that is, your virtues, your good works, your fastings, your vigils, and your prayers.
Why do not the wise children of this world reveal their material wealth? For two reasons: So that thieves would not hear of it and not to provoke the envy of evil men. There also exist envious and jealous thieves after spiritual treasure. They are the spirits of envy. As soon as you reveal your spiritual treasure, they will endeavor to belittle it and to squander it. Just as soon as you reveal it without need [let us say, out of vanity, so as to be praised], they have seized it and disparaged it; and you, O rich man of spiritual treasure, will imperceptibly and suddenly become a poor man. Many who were spiritually rich, the saints, made themselves out to be fools before the world so that by appearing foolish, they would conceal their great wisdom and strength within themselves. The Abba Isaiah writes, “Those good works which are performed in secret are more pleasing to God.” St. Nilus of Sinai says, “The covered skin of the body is white, but the uncovered skin in parched and black.” So it is with our concealed and revealed good works.