Gregory the Great, on Isa 56:11

“And meet impudent dogs, they never had enough: the shepherds themselves knew no understanding: all have turned aside into their own way, every one after his own gain, from the first even to the last.”

“For often improvident rulers, fearing to lose human favour, shrink timidly from speaking freely the things that are right; and, according to the voice of the Truth, serve unto the custody of the flock by no means with the zeal of shepherds, but in the way of hirelings; since they fly when the wolf cometh if they hide themselves under silence. For hence it is that the Lord through the prophet upbraids them, saying, "Dumb dogs, that cannot bark." Hence again He complains, saying, "Ye have not gone up against the enemy, neither opposed a wall for the house of Israel, to stand in the battle in the day of the Lord."”

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