Gregory the Great — as excerpted in the Catena Aurea on Mark 9:14-29

“(Mor. x. 30) But he who is freed from the power of the evil spirit is thought to be dead; for whosoever has already subdued earthly desires, puts to death within himself his carnal mode of life, and appears to the world as a dead man, and many look upon him as dead; for they who know not how to live after the Spirit, think that he who does not follow after carnal pleasures is altogether dead.”