Fasting was, in the Old Dispensation, one of the great means of making atonement; it was called “to afflict the soul;” but to be acceptable it had to be accompanied by sentiments of sorrow for sin and mercy towards others. Under the New Law, fasting is an earnest of grief and of penance. The Apostles do not fast as ong as the Bridegroom is with them, but they will fast when He is gone. Our Lord, wishing to expiat our sins, fasted forty days and forty nights, and taught His Apostles that certain evil spirits cannot be cast out except b prayer and fasting. True to His teachings, the Church has established the Lenten Fast, that of the Vigils and of the Ember Days to offer her children the opportunity of making expiation for their faults. Many a sin takes its rise directly or indirectly in the craving for pleasure, in excess in eating and drinking, and nothing is so effective in making atonement as mortification in eating, reaching as it does the very root of the evil by mortifying the craving for sensual pleasure. This is why the Saints have made a practice of fasting even outside the seasons appointed by the Church. Generous Christian souls imitate them and, if they cannot keep the strict fast, forego some food at each meal in order thus to curb their sensuality.
Fasting on bread and water one day a week (Wednesdays) is recommended for those who can do so. The practice is offered up for the reparation of sin, for grave offenses against God's Holy Will. Abstaining from meat on Fridays is also a traditional practice of mortification for sin.