Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 9:14-29

“He also permits the child to be vexed, that in this way we might know the devil’s wickedness, who would have killed him, had he not been assisted by the Lord. It goes on: And he asked his father, How long is it ago since this came unto him? And he said, Of a child; and offtimes it has cast him into the fire and into the waters to destroy him.”