“Then I saw in my dream that the Interpreter took Christian by the hand and led him into a room where there was a fireplace. The flames from the fireplace grew larger and hotter even though there was someone continually throwing water on it to try to quench it.
Then said Christian, ‘What does this mean?’
The Interpreter answered, ‘This fire is the work of grace that God accomplishes in the heart; he who throws water on the flames to try to extinguish it is the Devil. But as you see, the fire burns higher and hotter despite his efforts to put it out. Now let me show the reason for that.’
So the Interpreter took Christian to the other side of the wall, where he saw a Man with a vessel of oil in His hand, from which He secretly funneled oil into the fire.
Then Christian asked, ‘What does this mean?’
The Interpreter answered, ‘This is Christ who continually, with the oil of His grace, maintains the work already begun in the heart. No matter what the Devil tries to do, the gracious work that Christ is doing in the souls of His people only increases. You saw that the Man stood behind the wall to maintain the fire; that is to teach you that it is hard for the one being tempted to see how this work of grace is maintained in the soul.'”
–John Bunyan, The Pilgrim’s Progress (Wheaton: Crossway, 2009), 52.