Dear Susanna:

Well, it is enough that the Spiritual Works of Mercy is official teaching. There does not need to be a Bible verse.

2247 The works of mercy are charitable actions by which we come to the aid of our neighbor in his spiritual and bodily necessities (Isa 58:6-7; Heb 13:3). Instructing, advising, consoling, comforting are spiritual works of mercy, as are forgiving and bearing wrongs patiently. The corporal works of mercy consist especially in feeding the hungry, sheltering the homeless, clothing the naked, visiting the sick and imprisoned, and burying the dead Mt 25:31-46). Among all these, giving alms to the poor is one of the chief witnesses to fraternal charity: it is also a work of justice pleasing to God (Tob 4:5-11; Sir 17:22; Mt 6:2-4):

He who has two coats, let him share with him who has none and he who has food must do likewise (Lk 3:11). But give for alms those things which are within; and behold, everything is clean for you (Lk 11:41). If a brother or sister is ill-clad and in lack of daily food, and one of you says to them, "Go in peace, be warmed and filled," without giving them the things needed for the body, what does it profit? (Jas 2:15-16; 1 Jn 3:17)

The traditional wording of the Spiritual Works of Mercy are:

    *  To instruct the ignorant;
    * To counsel the doubtful;
    * To admonish sinners;
    * To bear wrongs patiently;
    * To forgive offences willingly;
    * To comfort the afflicted;
    * To pray for the living and the dead.

Admonishing the sinner refers to Fraternal Correction. The 1917 Catholic Encyclopedia states:

Fraternal correction is here taken to mean the admonishing of one's neighbor by a private individual with the purpose of reforming him or, if possible, preventing his sinful indulgence. This is clearly distinguishable from an official disciplining, whose mouthpiece is a judge or other like superior, whose object is the punishment of one found to be guilty, and whose motive is not so directly the individual  advantage of the offender as the furtherance of the common good. That there is, upon occasion and with due regard to circumstances, an obligation to administer fraternal correction there can be no doubt. This is a conclusion not only deducible from the natural law binding us to love and to assist one another, but also explicitly contained in positive precept such as the inculcation of Christ: "If thy brother shall offend against thee, go, and rebuke him between thee and him alone. If he shall hear thee, thou shalt gain thy brother" (Matthew 18:15). Given a sufficiently grave condition  of spiritual distress calling for succour in this way, this commandment  may exact fulfilment under pain of mortal sin. This is reckoned to be so only when

    * the delinquency to be corrected or prevented is a grievous one;
    * there is no good reason to believe that the sinner will adequately provide for himself;
    * there is a well-founded expectation that the admonition will be heeded;
    * there is no one else just as well fitted for this work of Christian charity and likely to undertake it;
    * there is no special trouble or disadvantage accruing to the reformer as a result of his zeal.

Practically, however, individuals without any official capacity are seldom impeachable as having seriously transgressed the law in this matter because it is but rarely one finds the coalition of circumstances just enumerated.

Of course the reproof is to be administered privately, i.e. directly to the delinquent and not in the presence of others. This is plainly the method appointed by Christ in the words just cited and only as a remedy for obduracy is any other contemplated by Him. Still there are occasions upon which one might lawfully proceed in a different way. For instance

    * when the offence is a public one;
    * when it makes for the prejudice of a third party or perhaps even the entire community;
    * when it can only be condignly dealt with by the authority of a superior paternally exercised;
    * when a public rebuke is necessary to preclude scandal: witness the withstanding of Peter by Paul mentioned in the Epistle to the Galatians (2:11-14);
    * when the offender has already in advance relinquished whatever right he possessed to have his good name safeguarded, as is the custom in some religious bodies.

The obligation of fraternal correction, so far as private persons go, does not obtain, generally speaking, for the case of one who violates a law through invincible ignorance. The obvious reason is that there is then no immunity for it is their duty to instruct their subordinates. Every one, however, whether having an official competency or not, is bound to give the admonition when the sin, committed though it be from ignorance, is hurtful to the offender or a third party or is the occasion of scandal.

Further, the Catechism teaches that it is possible to be accomplice to another's sin in certain situations:

1868 Sin is a personal act. Moreover, we have a responsibility for the sins committed by others when we cooperate in them:

- by participating directly and voluntarily in them;

- by ordering, advising, praising, or approving them;

- by not disclosing or not hindering them when we have an obligation to do so;

- by protecting evil-doers.

1869a Thus sin makes men accomplices of one another and causes concupiscence, violence, and injustice to reign among them.

Specifically on the issue of admonishing there are verses like the following:

(Titus 3:10-11)  As for a man who is factious, after admonishing him once or twice, have nothing more to do with him, knowing that such a person is perverted and sinful; he is self-condemned.

(2 Thess 3:14-15)  If any one refuses to obey what we say in this letter, note that man, and have nothing to do with him, that he may be ashamed. Do not look on him as an enemy, but warn him as a brother.

God Bless,
Bro. Ignatius Mary