Part — Wouters, Manual of Moral Theology
Part II. On the Necessity of the Act of Doing Penance
The act of doing penance is necessary by necessity both of means and of precept.
I. Necessity of means. We are not asking whether God, absolutely speaking, can remit sin to one who does not repent - concerning which there is dispute - but we are asking whether, in the present order of Providence, penance is necessary for the sinner. Now then: some penance1 is necessary by necessity of means for those fallen into mortal sin. This is clear:
From Sacred Scripture, which presents penance as a necessary condition for obtaining remission.2
From the Council of Trent: "Penance was indeed necessary at all times for all men who had defiled themselves by some mortal sin, in order to obtain grace and justice, even for those who had sought to be washed by the sacrament of Baptism, so that, perversity having been cast off and amended, they might detest so great an offense of God with hatred of sin and pious sorrow of soul."3
From the holy Fathers. Thus teach, for example, St. Ambrose,4 St. Augustine,5 St. Jerome.6
From the reason of fittingness. For it is not fitting that sin, that is, an injury inflicted upon God, be remitted unless the sinner repairs it - which is done by detesting it - and now wills not to afflict God with a new injury (St. Thomas, 3, question 86, article 2).
In what way the proposition proved can be reconciled with the certain doctrine which teaches that an act of charity justifies is explained in n. 282.
1 Namely, perfect contrition, or imperfect contrition together with the sacrament, or - as others add - together with martyrdom.
2 Cf. Sirach 2:22; Ezekiel 18:21-32; Luke 13:5; Matthew 3:7; Acts 3:19.
4 Letter 51, n. 11 (Migne, Patrologia Latina, vol. 16, col. 1162).
5 Letter 93, chapter 13, n. 53 (ed. Gaume, vol. 2, col. 377).
6 Commentary on Ecclesiastes 8:12 (Migne, Patrologia Latina, vol. 23, col. 1077 C).
II. Necessity of precept. This brings it about that he who neglects the act of doing penance not only does not obtain justification, but also commits a new sin.
The existence of the precept is clear from the fact that penance is prescribed in the Scriptures by imperative words.1 Next, every act necessary by necessity of means is also prescribed. Finally, reason dictates that an injury inflicted upon God must be repaired.
The object of the precept. The precept obliges either to an act of perfect contrition in the absence of the sacrament, or at least to attrition with the sacrament of Penance (or of Baptism as regards an unbeliever); likewise to undergoing the punishments inflicted by God because of sin. It seems that, in itself, no special precept is given of taking away or lessening the debts of temporal punishment, so that in itself the sinner does not sin who defers the expiation of the temporal punishment owed into the other life. I said in itself, because often from elsewhere there is an obligation of doing works which in fact diminish temporal punishment.
The time of the obligation. The precept of doing penance obliges the sinner:
a) In itself, that is, by reason of penance itself: 1. in danger of death or madness, because one who then neglects penance is judged in no way to will it. 2. It is disputed whether, in itself, there is an obligation not to defer penance for a long time after sin has been committed. St. Alphonsus rightly holds the negative opinion as sufficiently probable (VI, 437); for if a long delay of reparation owed to God is injurious, it seems that the same, by the same right, must be said of every delay. But no one admits that.
b) By accident, that is, by reason of another virtue: 1. when someone must or wishes to confect a sacrament; 2. when someone must or wishes to receive a sacrament of the living; 3. when someone would suffer grave temptations which he believed he could not resist unless he elicits an act of contrition; likewise, 4. when generally the delay of penance would expose someone to grave danger of sinning gravely. Concerning this, note these words of St. Thomas: without sanctifying grace, "that one remain for a long time without mortal sin is not possible" (1-2, question 109, article 8); likewise these words of St. Gregory: "Sin... which penance does not quickly wash away... by its own weight soon draws one to another";2 5. when the precept of charity toward God urges, and the memory of sin occurs to the sinner (St. Alphonsus, VI, 437). "Nevertheless, I do not deny that sinners, especially the rude, can for the most part, indeed almost always, be excused from this sin of delayed penance by reason of lack of advertence" (St. Alphonsus, loc. cit., doubt 1).
2 Moralia, book 25, chapter 9, n. 22; in Migne, Patrologia Latina, vol. 76, col. 334. St. Alphonsus, having considered this cause, judges a delay for the space of one year excessive (VI, 437, doubt 1).
Corollary I. One who neglects penance obligatory from the virtue of penance commits the sin of impenitence; one who omits penance prescribed from another source sins against that virtue from which penance is prescribed.
Corollary II. The faithful can indeed be taught the obligation of not deferring penance for a long time; nevertheless no statement should be made about a span of time which would constitute grave sin. Besides this, they should be stirred up to elicit perfect contrition every morning and evening, and also soon after committing a grave sin.