The Gospels say: "But when you fast, anoint your head and wash your face" (Matthew 6:17). What does this mean and how do Christians fast?
Answer: The verse quoted in the question is part of a section of the Gospel according to St Matthew (6:1-18) in which Jesus speaks of the big trinity of “Alms, Prayer and Fasting”, as they have developed through the Old Testament as the expression of true piety. According to Jesus these three dimensions are to be practiced in private, i.e. they are not to become subject of demonstrative self-righteousness and piety, a danger which cannot be ignored. Jesus, too, preaches about Fasting in private (Matthew 6:16-18):
"When you are fasting, do not look gloomy like the hypocrites! They neglect their appearance so that they may appear to others to be fasting. Amen, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, so that you may not appear to be fasting, except to your Father who is hidden. And your Father who sees what is hidden will repay you."
The details of this sermon from Jesus are not important, as long as the main point is not lost: fasting is aimed towards God and not towards other people. It demands faith and the will to an inner turning or returning towards God. Furthermore, fasting is not to be seen as a mere ascetic exercise: "This, rather, is the fasting that I wish: releasing those bounded unjustly, untying the thongs of the yoke; setting free the oppressed, breaking every yoke; Sharing your bread with the hungry, sheltering the oppressed and the homeless; Clothing the naked when you see them, and not turning your back on your own." (Isaiah 58,6f.) It is all about God, who is life and creates life, who leads the way out of all kinds of slavery into the promised land, the Kingdom of God, where all people are brothers and sisters.
At issue is therefore not primarily the outer exercise of fasting, but the conversion of the heart, the inner repentance. Without this, all actions external expression of repentance will remain barren and dishonest. The inner conversion, however, demands to be expressed through visible signs, actions and acts of repentance. (Joel 2:12-13; Isaiah 1:16-17; Matthew 6:1-6;16-18). Inner repentance is a radical new direction given to every aspect of life, conversion, a wholehearted returning to God, desisting from sin, a renouncing of evil, as well as an aversion against the sins we have committed. At the same time it brings with it the desire and the decision to change ones life, as well as the hope for God’s mercy and the trust in his mercy.
Christian inner repentance can find many different kinds of expression. The Bible and the patriarchs speak in the main of the three above mentioned expressions: fasting, prayer and the giving of alms, as expressions of repentance before oneself, before God and before fellow humans. Next to the deep catharsis effected through Baptism and martyrdom, forgiveness of sin can also be achieved through efforts for reconciliation with ones neighbor, the tears of repentance, the care for the wellbeing of ones neighbor, the intercessions from the Saints and active charity – "because love covers a multitude of sins" (1 Peter 4:8).
The periods of repentance in the course of the liturgical year (i.e. the year according to the Church’s calendar), in other words: the days of fasting, each Friday in memory of the death of our Lord are formative periods in the Church’s life of repentance. These times are particularly suited to retreats, liturgies of repentance, pilgrimages, voluntary denial for example through fasting or charitable giving, and sharing with others (charitable and missionary).
The Church’s rules for fasting
The period of fasting before Easter, Lent, is aimed at the spiritual preparation for the celebration of the saving death and the resurrection of Jesus. Desisting from loud music and entertainment shall create the space for the necessary peace and quiet for this preparation.
Days of abstinence and/or repentance are all Fridays in a year. During Lent Catholic Christians should abstain from meat. On all other Fridays in the year Christians can either abstain from meat or perform another act of spiritual or physical charity. The deliberate choice of simple foods or abstention from luxury foods and entertainment both fulfill the abstinence requirement. Abstinence becomes compulsory from 14 years of age until the end of life.
According to the “Catechism of the Catholic Church” (No 2447), acts of charity are: The works of mercy are charitable actions by which we come to the aid of our neighbor in his spiritual and bodily necessities (cf. Isaiah 58:6-7).
Days of fasting are Ash Wednesday and Good Friday. On those strict days of fasting Catholic Christians should refrain from eating any meat at all, should eat as simply as possible and be satisfied with one main meal (and at the most two small snacks). Those days should as far as possible be spent in silence, in increased prayer and include attending Worship. Fasting includes a noticeable abstention from food. A major part of the requirements for those two days are the abstention from loud music, dancing and entertainment. Fasting becomes compulsory from 18 years of age until the beginning of the 60th year.