“Fasting is not a mere matter of diet. It is moral as well as physical. True fasting is to be converted in heart and will; it is to return to God, to come home like the Prodigal to our Father’s house. In the words of St. John Chrysostom, it means ‘abstinence not only from food but from sins’. ‘The fast’, he insists, ‘should be kept not by the mouth alone but also by the eye, the ear, the feet, the hands and all the members of the body’: the eye must abstain from impure sights, the ear from malicious gossip, the hands from acts of injustice. It is useless to fast from food, protests St. Basil, and yet to indulge in cruel criticism and slander: ‘You do not eat meat, but you devour your brother’. The same point is made in the Triodion, especially during the first week of Lent:
As we fast from food, let us abstain also from every passion…..
Let us observe a fast acceptable and pleasing to the Lord.
True fasting is to put away all evil,
To control the tongue, to forbear from anger,
To abstain from lust, slander, falsehood and perjury.
If we renounce these things, then is our fasting true and acceptable to God.
Let us keep the Fast not only by refraining from food,
But by becoming strangers to all the bodily passions.
The inner significance of fasting is best summed up in the triad: prayer, fasting, almsgiving. Divorced from prayers and from the reception of the holy sacraments, unaccompanied by acts of compassion, our fasting becomes pharisaical or even demonic. It leads, not to contrition and joyfulness, but to pride, inward tension and irritability.”
(The Lenten Triodion translated by Mother Mary and Archimandrite Kallistos Ware, pp 17-18