From a couple of the church fathers on the difference between a true shepherd of the sheep and a hireling; a sobering reminder for those who are called to be pastors of Christ's flock:
"There are some who love earthly possessions more than the sheep and do not deserve the name of a shepherd. He is called a hireling and not a shepherd because he does not pasture the Lord's sheep out of his deep love for them but for a temporal reward. That person is a hireling who holds the place of shepherd but does not seek to profit souls. He is eager for earthly advantages, rejoices in the honor of preferment, feeds on temporal gain and enjoys the deference offered him by other people" (Gregory the Great).
"But we cannot truly know whether anyone is a shepherd or a hireling if there is no occasion to test him. During times of peace even a hireling frequently stands for the protection of the flock like a true shepherd. When the wolf comes, each one shows what his intention was as he stood as protector of the flock" (Gregory the Great).
"The evil spirit goes about attacking the sheepfolds of believers, seeking the death of souls; ceaselessly, every day, he tears apart minds more than bodies. Of this wolf it is said, 'And the wolf snatches and scatters the sheep.' The wolf comes, and the hireling flees. The evil spirit tears apart the minds of believers in temptation, and the one holding the place of shepherd does not take responsiblity. Souls are perishing, and he enjoys earthly advantages. The wolf snatches and scatters the sheep when he entices one to drunkenness, inflames another with greed, exalts another by pride, destroys another by anger, stirs one up by envy, trips up another by deceit. When the devil slays believers through temptations, he is like a wolf dispersing the flock. No zeal rouses the hireling against these temptations, no love excites him. He seeks only the outward advantage and carelessly allows the inward injury to his flock" (Gregory the Great).
"Suppose someone has sinned — grievously sinned. He ought to be rebuked, excommunicated. However, if he is excommunicated, he will become an enemy and will plot and do as much harm as he can. And so, for the time being, the pastor who seeks his own and not what is Christ's keeps quiet and does not reprove the person so that he will not have to put up with the annoyances of their attacks or lose what he truly follows after — the advantage of human friendship. But look! The wolf has caught a sheep by the throat; the devil has enticed a believer into adultery. And yet, you are silent — you do not censure. As a hireling, you have seen the wolf coming, and you fled. Perhaps you answer and say, 'See, I am here; I have not fled.' You have fled because you have been silent; you have been silent because you are afraid" (Augustine of Hippo).
"The wolf too comes upon the sheep whenever any unrighteous person oppresses the humble believers. The one who only appears to be a shepherd leaves the sheep and flees because he is too afraid to resist the wolf's violence from fear of danger to himself. He flees not by moving to another place but by withholding consolation from his flock. The one who conceals himself beneath his silence is the one who flees. The hireling is inflamed with no enthusiasm to fight against this injustice. A person who is in charge of the sheep, not because he loves them but because he is seeking earthly gain, cannot make a stand when the sheep are in danger. Because he esteems honor, because he enjoys his temporal advantages, he is afraid to oppose the danger for fear he should lose what he loves so much" (Gregory the Great).
(Excerpts from the Ancient Christian Commentary on Scripture: New Testament IVa, John 1-10, edited by Joel C. Elowsky; InterVarsity, 2006)