The *Catechism of the Catholic Church * defines penance: Interior penance: a conversion of heart toward God and away from sin, which implies the intention to change one’s life because of hope in divine mercy. External acts of penance include fasting, prayer, and almsgiving. The observance of certain penitential practices is obliged by the fourth precept of the Church.
Paragraph 1438 of the catechism discusses Fridays and lists several forms of penance: “The seasons and days of penance in the course of the liturgical year (Lent, and each Friday in memory of the death of the Lord) are intense moments of the Church’s penitential practice. These times are particularly appropriate for spiritual exercises, penitential liturgies, pilgrimages as signs of penance, voluntary self-denial such as fasting and almsgiving, and fraternal sharing (charitable and missionary works).”
(Note that on all Fridays during Lent abstinence is required. On Ash Wednesday and Good Friday abstinence and fasting are required.)
