Didymus the Blind, on Acts 20:28

“Take heed to yourselves, and to the whole flock, wherein the Holy Ghost hath placed you bishops, to rule the church of God, which he hath purchased with his own blood.”

“"Take care for yourselves and for the entire flock," and the following. Since it is not according to nature but according to an appropriation of the power that comes from the Spirit that a person is ordained to the episcopacy by the Holy Spirit for our sake, it is possible for one holding such a position to fall from it, without due care. For if someone were established as a shepherd of the church because of the state of his being, that person would hold whatever office without possibility of change. But it not only says that bishops must pay heed to themselves but also to the flock that the Savior acquired by his blood. And just as he will not fall if he is attentive to himself by taking care for both the requisite virtues and his faith—that is, he will neither start speaking the perverse things of heresies nor follow selfish ambition by attempting to lure Christ's disciples away in order to imitate himself and follow him—so also he must take care for the flock by turning away from it the wolves who are falsely called apostles and who, being ravenous, live on the ruin of the flock.… Now he turns away these wolves, if he, established by the Holy Spirit to oversee the church, is a good shepherd. A hired man, not being a shepherd, flees when a wolf comes to scatter and kill the sheep. Furthermore, a hired man is no shepherd, since he takes charge of the community for profit and pay, and not come what may. So it is to be realized that the Holy Spirit establishes shepherds and bishops for the church just as God establishes in the church "first apostles," and the following.”

Imported from an open dataset — not yet checked against the printed edition.