Pope St. Gregory I: Liber Regulae Pastorlis
No one presumes to teach an art till he has first, with intent meditation, learnt it.
What rashness is it, then, for the unskillful to assume pastoral authority, since the government of souls is the art of arts! For who can be ignorant that the sores of the thoughts of men are more occult than the sores of the bowels?
And yet how often do men who have no knowledge whatever of spiritual precepts fearlessly profess themselves physicians of the heart, though those who are ignorant of the effect of drugs blush to appear as physicians of the flesh!
But because, through the ordering of God, all the highest in rank of this present age are inclined to reverence religion, there are some who, through the outward show of rule within the holy Church, affect the glory of distinction. They desire to appear as teachers, they covet superiority to others, and, as the Truth attests, they seek the first salutations in the market-place, the first rooms at feasts, the first seats in assemblies (Matt 23:6, 7), being all the less able to administer worthily the office they have undertaken of pastoral care, as they have reached the magisterial position of humility out of elation only.
For, indeed, in a magisterial position language itself is confounded when one thing is learnt and another taught. Against such the Lord complains by the prophet, saying, "They have reigned, and not by Me; they have been set up as princes, and I knew it not" (Hos. 8:4). For those reign of themselves, and not by the Will of the Supreme Ruler, who, supported by no virtues, and in no way divinely called, but inflamed by their own desire, seize rather than attain supreme rule. But them the Judge within both advances, and yet knows not; for whom by permission He tolerates them surely by the judgment of reprobation He ignores. Whence to some who come to Him even after miracles He says, "Depart from Me, ye workers of iniquity, I know you not who ye are" (Luke 13:27).
The unskillfulness of shepherds is rebuked by the voice of the Truth, when it is said through the prophet, "The shepherds themselves have not known understanding" (Is. 56:11); whom again the Lord denounces, saying, "And they that handle the law knew Me not" (Jer. 2:8).
And therefore the Truth complains of not being known of them, and protests that He knows not the principality of those who know not Him; because in truth these who know not the things of the Lord are unknown of the Lord; as Paul attests, who says, "But if any man knoweth not, he shall not be known (1 Cor. 14:38).
Yet this unskillfulness of the shepherds doubtless suits often the deserts of those who are subject to them, because, though it is their own fault that they have not the light of knowledge, yet it is in the dealing of strict judgment that through their ignorance those also who follow them should stumble. Hence it is that, in the Gospel, the Truth in person says, "If the blind lead the blind, both fall into the ditch" (Matt. 15:14). Hence the Psalmist (not expressing his own desire, but in his ministry as a prophet) denounces such, when he says, "Let their eyes be blinded that they see not, and ever bow thou down their back" (Ps. 68:24).
For, indeed, those persons are eyes who, placed in the very face of the highest dignity, have undertaken the office of spying out the road; while those who are attached to them and follow them are denominated backs. And so, when the eyes are blinded, the back is bent, because, when those who go before lose the light of knowledge, those who follow are bowed down to carry the burden of their sins.