Were the Redeemer to descend into a church, and sit in a confessional to administer the sacrament of penance, and a priest to sit in another confessional, Jesus would say over each penitent, ‘Ego te absolvo,’ the priest would likewise say over each of his penitents, ‘Ego te absolve’, and the penitents of each would be equally absolved. […] The priest holds the place of the Saviour himself, when, by saying ‘Ego te absolvo’ he absolves from sin. This great power, which Jesus Christ has received from his eternal Father, he has communicated to his priests. ‘Jesus,’ says Tertullian, ‘invests the priests with his own powers.’ (Saint Alphonsus de Liguori, Dignity and duties of the priest or Selva, part I cap.I. no. 8, pg. 34)

From the institution of the sacrament of penance as already explained the universal Church has always understood that the complete confession of sins was also instituted by our Lord, (Jas 5:16 Jn 1:9), and by divine law is necessary for all who have fallen after baptism [can. 7], because our Lord Jesus Christ, when about to ascend from earth to heaven, left behind Him priests as His own vicars (Mt 16:19, Mt 18:18, Jn 20:23), as rulers and judges, to whom all the mortal sins into which the faithful of Christ may have fallen should be brought, so that they in virtue of the power of the keys may pronounce the sentence of remission or retention of sins. (Denzinger-Hünermann 1679. Council of Trent, Session XIII, Doctrine on the Sacrament of penance, October 11, 1551)

It also teaches that even priests who are bound by mortal sin exercise as ministers of Christ the office of forgiving sins by virtue of the Holy Spirit conferred in ordination, and that they are of an erroneous opinion who contend that this power does not exist in bad priests. (Denzinger-Hünermann 1684. Council of Trent, Session XIV, Doctrine on the Sacrament of Penance, Ch. 6, November 25, 1551)

These truths are all the more evident inasmuch as we exercise the priestly ministry not in our own name, but in the name of Jesus Christ. The Apostle said: Let man so consider us as the ministers of Christ and the dispensers of the mysteries of God; for Christ, therefore, we are ambassadors. This is the reason that Christ has numbered us not among his servants but as his friends. (Pius X. Apostolic Exhortation Haerent animo, no. 4, August 4, 1908)

Now the minister, by reason of the sacerdotal consecration which he has received, is made like to the High Priest and possesses the power of performing actions in virtue of Christ’s very person. Wherefore in his priestly activity he in a certain manner ‘lends his tongue, and gives his hand’ to Christ (Saint John Chrysostom, In Joann. Hom., 86:4). (Pius XII. Encyclical Mediator Dei, no. 69, November 20, 1947)

Just as in Baptism an ‘exchange of clothing’ is given, an exchanged destination, a new existential communion with Christ, so also in priesthood there is an exchange: in the administration of the sacraments, the priest now acts and speaks ‘in persona Christi’. In the sacred mysteries, he does not represent himself and does not speak expressing himself, but speaks for the Other, for Christ. (Benedict XVI. Homily for the Chrism Mass, April 5, 2007)

In order to understand what it means for the priest to act in persona Christi Capitis in the person of Christ the Head and to realize what consequences derive from the duty of representing the Lord, especially in the exercise of these three offices, it is necessary first of all to explain what ‘representation’ means. The priest represents Christ. What is implied by ‘representing’ someone? In ordinary language it usually means being delegated by someone to be present in his place, to speak and act in his stead because the person he represents is absent from the practical action. Let us ask ourselves: does the priest represent the Lord in this way? The answer is no, because in the Church Christ is never absent, the Church is his living Body and he is the Head of the Church, present and active within her. […] Therefore the priest, who acts in persona Christi Capitis and representing the Lord, never acts in the name of someone who is absent but, rather, in the very Person of the Risen Christ, who makes himself present with his truly effective action. He really acts today and brings about what the priest would be incapable of: the consecration of the wine and the bread so that they may really be the Lord’s presence, the absolution of sins. (Benedict XVI. General audience, April 14, 2010)

[The priest] when he raises his hand in blessing and pronounces the words of absolution, he acts ‘in persona Christi’ – in the person of Christ – not simply as Christ’s representative, but also and above all as a human instrument in which the Lord Jesus – God-with-us – is present and acts. (John Paul II. General audience, no. 2, February 22, 1984)

The Lord Jesus has thus become ‘our reconciliation’ (cf. Rom 5:11) and our ‘peace’ (cf. Eph 2:14). The Church, then, through the priest in a singular manner, does not act as if it were an autonomous reality: it structurally depends on the Lord Jesus who has founded it, inhabits and acts in it, in such a way that he makes present, in different times and in diverse places, the mystery of the Redemption. The evangelical word clarifies this ‘being sent’ of the Church through his Apostles by Christ, for the remission of sins. ‘As my Father sent me’, affirmed the resurrected Lord Jesus Christ, ‘I send you’. And after saying this, breathing over them he added: ‘Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained’ (Jn 20:21 – 22). In this way, then, behind – or within – the human reality of the priest, the same Lord who has ‘authority on earth to forgive sins’ (Lk 5:24) hides and acts, and that with this finality ‘he deserved’(cf. Jn 7:39) and ‘sent’ (cf. Jn 20:22) ‘his Spirit’ (cf. Rom 8:9) after the Sacrifice of Calvary and of the victory of Easter. (John Paul II. General audience, March 28, 1984)

The bishop or the priest, in the exercise of his ministry, does not act in his own name, in persona propria; he represents Christ, who acts through him: ‘The priest truly acts in the place of Christ’, as Saint Cyprian already wrote in the third century. It is the ability to represent Christ that Saint Paul considered as characteristic of his apostolic function (cf. 2Cor 5:20; Gal 4:14). […] If one does justice to these reflections, one will better understand how well-founded is the basis of the Church’s practice; and one will conclude that the controversies raised in our days […] are for all Christians a pressing invitation to meditate on the mystery of the Church, to study in greater detail the meaning of the episcopate and the priesthood, and to rediscover the real and preeminent place of the priest in the community of the baptized, of which he indeed forms part but from which he is distinguished because, in the actions that call for the character of ordination, for the community he is – with all the effectiveness proper to the sacraments – the image and symbol of Christ himself who calls, forgives, and accomplishes the sacrifice of the Covenant. (Denzinger-Hünermann 4599, 4602. Congregation for the Doctrine of the Faith, Declaration Inter insignioris, Ch. V, October 15, 1976)

Priests act especially in the person of Christ as ministers of holy things, particularly in the Sacrifice of the Mass. […] In like fashion they are united with the intention and love of Christ when they administer the sacraments. This is true in a special way when in the performance of their duty in the sacrament of Penance they show themselves altogether and always ready whenever the sacrament is reasonably sought by the faithful. (Vatican Council II. Decree Presbyterorum ordinis, no. 13, December 7, 1965)

Only God forgives sins (cf. Mk 2:7). Since he is the Son of God, Jesus says of himself: ‘The Son of man has authority on earth to forgive sins’ and exercises this divine power; ‘Your sins are forgiven’ (cf. Mk 2:5, 10; Lk 7:48). Further, by virtue of his divine authority he gives this power to men to exercise in his name (cf. Jn 20:21 – 23). (Catechism of the Catholic Church, no. 1441)

But if we look to its ministers, or to the manner in which it is to be exercised, the extent of this divine power will not appear so great; for our Lord gave not the power of so sacred a ministry to all, but to Bishops and priests only. The same must be said regarding the manner in which this power is to be exercised; for sins can be forgiven only through the Sacraments, when duly administered. The Church has received no power otherwise to remit sin. Hence it follows that in the forgiveness of sins both priests and Sacraments are, so to speak, the instruments which Christ our Lord, the author and giver of salvation, makes use of, to accomplish in us the pardon of sin and the grace of justification. […] This wonderful and divine power was never communicated to creatures, until God became man. Christ our Saviour, although true God, was the first one who, as man, received this high prerogative from His heavenly Father. That you may know that the son of man hath power on earth to forgive sins (then said he to the man sick of the palsy), rise. take up thy bed, and go into thy house. As, therefore, He became man, in order to bestow on man this forgiveness of sins, He communicated this power to Bishops and priests in the Church, previous to His Ascension into heaven, where He sits forever at the right hand of God. Christ, however, as we have already said, remits sin by virtue of His own authority; all others, by virtue of His authority delegated to them as His ministers. If, therefore, whatever is the effect of infinite power claims our highest admiration and reverence, we must readily perceive that this gift, bestowed on the Church by the bounteous hand of Christ our Lord, is one of inestimable value. (Catechism of the Council of Trent, 1100)

The head influences the other members in two ways. First, by a certain intrinsic influence, inasmuch as motive and sensitive force flow from the head to the other members; secondly, by a certain exterior guidance, inasmuch as by sight and the senses, which are rooted in the head, man is guided in his exterior acts. Now the interior influx of grace is from no one save Christ, Whose manhood, through its union with the Godhead, has the power of justifying; but the influence over the members of the Church, as regards their exterior guidance, can belong to others; […] differently, however, from Christ. First, inasmuch as Christ is the Head of all who pertain to the Church in every place and time and state; but all other men are called heads with reference to certain special places […] Christ is the Head of the Church by His own power and authority; while others are called heads, as taking Christ’s place, according to 2Cor 2:10, ‘For what I have pardoned, if I have pardoned anything, for your sakes I have done it in the person of Christ’, and 2Cor 5:20, ‘For Christ therefore we are ambassadors, God, as it were, exhorting by us’. (Saint Thomas Aquinas. Summa Theologica III, q. 8, a. 6)

I have told you all this, dearest daughter, that you may the better recognize the dignity to which I have called My ministers, so that your grief at their miseries may be more intense. […] No greater dignity exists in this life. They are My anointed ones, and I call them My Christs, because I have given them the office of administering Me to you, and have placed them like fragrant flowers in the mystical body of the holy Church. The angel himself has no such dignity, for I have given it to those men whom I have chosen for My ministers, and whom I have appointed as earthly angels in this life. (Saint Catherine of Siena. The Dialogue, Ch. 113)