14 Whoever, therefore, flees from danger in circumstances in which the Church is not deprived, through his flight, of necessary service, is doing that which the Lord has commanded or permitted. But the minister who flees when the consequence of his flight is the withdrawal from Christ's flock of that nourishment by which its spiritual life is sustained, is an “hireling who sees the wolf coming, and flees because he cares not for the sheep.”
With love, which I know to be sincere, I have now written what I believe to be true on this question, because you asked my opinion, my dearly beloved brother; but I have not enjoined you to follow my advice, if you can find any better than mine. Be that as it may, we cannot find anything better for us to do in these dangers than continually beseech the Lord our God to have compassion on us. And as to the matter about which I have written, namely, that ministers should not desert the churches of God, some wise and holy men have by the gift of God been enabled both to will and to do this thing, and have not in the least degree faltered in the determined prosecution of their purpose, even though exposed to the attacks of slanderers.
Source: Letters (New Advent)