(CG 4/76). Of the Episcopal Dignity, and that therein one Bishop is Supreme (Book 4. God, in His Revelation) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

NO agent can do anything in what is beyond his competence, unless he gets power from elsewhere: thus the mayor cannot put restraint upon the citizens except in virtue of the power that he receives from the king. But what is done in the Sacraments exceeds human competence. Therefore no one can administer the Sacraments, however good he may be, unless he receives power so to do. But the opposite of goodness is wickedness and sin. Therefore neither by sin is he hindered from the administration of the Sacraments, who has received power to do so.

5. One man cannot judge of the goodness or wickedness of another man: that is proper to God alone, who searches the secrets of hearts. If then the wickedness of the minister could hinder the effect of the Sacrament, it would be impossible for a man to have a sure confidence of his salvation: his conscience would not remain free from the sense of sin. But it is irrational for any one to have to rest the hope of his salvation on the goodness of a mere man: for it said, Cursed is the man who puts his trust in man (Jer. xvii, 5). In order then that we may rest the hope of our salvation on Christ, who is God and man, we must allow that the Sacraments work salvation in the power of Christ, whether they be administered by good or evil ministers.

Hence the Lord says: The Scribes and Pharisees have come to sit in the chair of Moses: whatever things therefore they say to you, observe and do: but according to their works do ye not (Matt. xxiii, 2).

Hereby is cast out the error of those who say that all good men can administer the Sacraments, and no bad men.