Raphael - The Transfiguration
“This is my beloved Son, in whom I am well pleased; hear ye him.”
Not long ago, someone asked me about the Catholic practice of doing penance—why do we do penance during Lent—and why do we do penance after going to Confession; aren't our sins forgiven by the Sacrament; why should we have to do anything more? So, perhaps, a few words are in order about the good that we receive from doing penance.
The dictionary defines penance as any “mortification, almsdeed, or other good work performed in the spirit of sorrow or hatred for sin.” Among the common penances that Catholics perform we might include prayer, fasting and abstinence, austerity, pilgrimage, retreats, physical mortification, charitable work, crusades, and missions.
We might say that the first reason for doing penance is to satisfy the divine justice for our sins. Simply stated, we have done something wrong, and now we must do something good to “balance the scales.” While this may seem a bit abstract, it is important to acknowledge this divine justice, and not to think of penance only in terms of benefits to men and mankind.
Doing penance is extremely important in order to maintain a proper spirit of humility. Remember, we said that virtually all sin has its roots in excessive and unjustified pride. The proud, of course, demand a great deal for themselves in terms of physical rewards and comforts. By giving up such things as food, and fancy clothing, and other material comforts we admit our lowliness and strengthen our humility. By practicing such austerities, we give up our own will in favor of doing God's will.
Certainly, most forms of penance help us to imitate Christ in His holy life and in His suffering on the Cross. There is probably no greater way to assure salvation than to try to be Christ-like. Living in the modern world, with all of its luxuries, cheerfully performing penance helps to detach us from the things that would draw us away from Christ.
Most of the time when we go to Confession, the priest assigns us a penance in the form of prayers: “Say so many Our Fathers or Hail Marys.” We ought to make a point of saying these prayers with attention and devotion. They are not just something to do as quickly as possible, but they are intended to draw us closer to God and farther away from sin. Many holy people recognize that “prayer is the sweetest form of penance,” as it takes very little effort on our part, but results in something that should always be satisfying; a brief experience of God Himself and a little taste of heaven.
Occasionally, people make pilgrimages as a means of penance. Now, of course such a trip should not be undertaken as one would a fancy vacation. Pilgrimages ought to include some elements of hardship and austerity; not the rich trappings of a tour that stays in first class hotels. Pilgrimages as penance have the added benefit of stirring up enthusiasm for the Faith, as people come together from distant places to honor Almighty God through His saints.
By the way, one of the best pilgrimages is also the least expensive. That is to make a visit to a church and spend some time with our Lord in the Blessed Sacrament. There isn't much point in travelling thousands of miles to reach a holy spot if you are not willing to visit our Lord who waits patiently in the nearby tabernacle.
Penance is by far and away the best way to develop self-control. If, through penance, we become used to denying ourselves some of the innocent pleasures we seek, and used to living with difficulties, we will have much less trouble in controlling our appetites for things that we must not have. It is hard to think of a better way to demonstrate “hatred of sin” than to practice what will keep us from sinning again in the future. That's what Saint Paul was telling the Thessalonians in today's epistle when he cautioned them to “possess [their] vessels in holiness.”
At one time people might go on a crusade as a means of doing penance. They would go, often at the risk of life and limb, to make the holy land and Christendom safe from the enemies of the faith. We don't see crusades much anymore, but perhaps they may become an important means of penance as Christians become a smaller and smaller percentage of the world's population.
Somewhat like the crusade is the idea of engaging in missionary activity and offering all of its many discomforts as penance. One has only to read the accounts of the missionaries who brought Christianity to the new world from Europe to be inspired with their heroic penance. Without this willingness to do penance, very little of the world would ever have become Catholic.
Finally, we might mention alms deeds. That is relief of the poor and the sick done for the love of Christ and done in His name. It also might include labor or donations to further the work of the Church and its many institutions. Public works of relief are particularly important in that they demonstrate the good influence that Christ and His Church have on us to those outside the Church.
So, we see that penance is an important part of our Catholic lives. Not only does it satisfy justice, in some way making up for the evils we have done, but it provides us with all of these wonderful fruits: humility, patience, enthusiasm for the faith, self control, charity for the poor, the growth of the Church, and even the spreading of the Faith to foreign lands.
Penance teaches us how to “possess our vessels in holiness,” and how to live “not unto uncleanness, but unto sanctification in Christ Jesus our Lord.”
 Gospel: Matthew xvii: 1-9 http://www.drbo.org/x/d?b=drb&bk=47&ch=17&l=1#x
 Epistle: 1 Thessalonians iv. 1-7 http://www.drbo.org/cgi-bin/d?b=drl&bk=59&ch=4&l=1-#x