I answer that, As stated above (A. 1), the ministers of the Church work instrumentally in the sacraments, because, in a way, a minister is of the nature of an instrument. But, as stated above (Q. 62, AA. 1, 4), an instrument acts not by reason of its own form, but by the power of the one who moves it. Consequently, whatever form or power an instrument has in addition to that which it has as an instrument, is accidental to it: for instance, that a physician's body, which is the instrument of his soul, wherein is his medical art, be healthy or sickly; or that a pipe, through which water passes, be of silver or lead. Therefore the ministers of the Church can confer the sacraments, though they be wicked.
Reply Obj. 1: The ministers of the Church do not by their own power cleanse from sin those who approach the sacraments, nor do they confer grace on them: it is Christ Who does this by His own power while He employs them as instruments. Consequently, those who approach the sacraments receive an effect whereby they are enlikened not to the ministers but to Christ.
Reply Obj. 2: Christ's members are united to their Head by charity, so that they may receive life from Him; for as it is written (1 John 3:14): "He that loveth not abideth in death." Now it is possible for a man to work with a lifeless instrument, and separated from him as to bodily union, provided it be united to him by some sort of motion: for a workman works in one way with his hand, in another with his axe. Consequently, it is thus that Christ works in the sacraments, both by wicked men as lifeless instruments, and by good men as living instruments.
Reply Obj. 3: A thing is required in a sacrament in two ways. First, as being essential to it: and if this be wanting, the sacrament is invalid; for instance, if the due form or matter be wanting. Secondly, a thing is required for a sacrament, by reason of a certain fitness. And in this way good ministers are required for a sacrament. _______________________
SIXTH ARTICLE [III, Q. 64, Art. 6]
Whether Wicked Men Sin in Administering the Sacraments?
Objection 1: It seems that wicked men do not sin in administering the sacraments. For just as men serve God in the sacraments, so do they serve Him in works of charity; whence it is written (Heb. 13:16): "Do not forget to do good and to impart, for by such sacrifices God's favor is obtained." But the wicked do not sin in serving God by works of charity: indeed, they should be persuaded to do so, according to Dan. 4:24: "Let my counsel be acceptable" to the king; "Redeem thou thy sins with alms." Therefore it seems that wicked men do not sin in administering the sacraments.
Obj. 2: Further, whoever co-operates with another in his sin, is also guilty of sin, according to Rom. 1:32: "He is [Vulg.: 'They are'] worthy of death; not only he that commits the sin, but also he who consents to them that do them." But if wicked ministers sin in administering sacraments, those who receive sacraments from them, co-operate in their sin. Therefore they would sin also; which seems unreasonable.
Obj. 3: Further, it seems that no one should act when in doubt, for thus man would be driven to despair, as being unable to avoid sin. But if the wicked were to sin in administering sacraments, they would be in a state of perplexity: since sometimes they would sin also if they did not administer sacraments; for instance, when by reason of their office it is their bounden duty to do so; for it is written (1 Cor. 9:16): "For a necessity lieth upon me: Woe is unto me if I preach not the gospel." Sometimes also on account of some danger; for instance, if a child in danger of death be brought to a sinner for baptism. Therefore it seems that the wicked do not sin in administering the sacraments.
On the contrary, Dionysius says (Eccl. Hier. i) that "it is wrong for the wicked even to touch the symbols," i.e. the sacramental signs. And he says in the epistle to Demophilus: "It seems presumptuous for such a man," i.e. a sinner, "to lay hands on priestly things; he is neither afraid nor ashamed, all unworthy that he is, to take part in Divine things, with the thought that God does not see what he sees in himself: he thinks, by false pretenses, to cheat Him Whom he calls his Father; he dares to utter, in the person of Christ, words polluted by his infamy, I will not call them prayers, over the Divine symbols."