Theophylact of Ohrid — as excerpted in the Catena Aurea on Luke 14:34-35

“But not only those who are gifted with the grace of teachers, but private individuals also He requires to become like salt, useful to those around them. But if he who is to be useful to others becomes reprobate, he cannot be profited, as it follows, But if the salt has lost his savour, where-with shall it be seasoned?”