By: St. John Cassian
What we gain from fasting does not compensate for what we lose through anger. Our profit from scriptural reading in no way equals the damage we cause ourselves by showing contempt for a brother. We must practice fasting, vigils, withdrawal, and the meditation of Scripture as activities which are subordinate to our main objective, purity of heart, that is to say, love, and we must never disturb this principal virtue for the sake of those others. If this virtue remains whole and unharmed within us nothing can injure us, not even if we are forced to omit any of those other subordinate virtues. Nor will it be of any use to have practiced all these latter if there is missing in us that principal objective for the sake of which all else is undertaken.
St. John Cassian (Conferences, Conf. One sect. 7; Paulist Press pg. 42)