C.S. Lewis writes about the necessity to kill sin, and the pain that can come with it, in The Great Divorce:
I saw coming toward us a Ghost who carried something on his shoulder. Like all the Ghosts, he was unsubstantial, but they differed from one another as smokes differ. Some had been whitish; this one was dark and oily. What sat on his shoulder was a little red lizard, and it was twitching its tail like a whip and whispering things in his ear. As we caught sight of him he turned his head to the reptile with a snarl of impatience. ‘Shut up, I tell you!’ he said. It wagged its tail and continued to whisper to him. He ceased snarling, and presently began to smile. Then he turned and started to limp westward, away from the mountains
‘Of so soon?’ said a voice.
The speaker was more or less human in shape but larger than a man, and so bright that I could hardly look at him. His presence smote on my eyes and on my body too (for there was heat coming from him as well as light) like the morning sun at the beginning of a tyrannous summer day.
‘Yes. I’m off,’ said the Ghost. ‘Thanks for all your hospitality. But it’s no god, you see. I told this little chap’ (here he indicated the Lizard) ‘that he’d have to be quiet if he came–which he insisted on doing. Of course his stuff won’t do here: I realise that. But he won’t stop. I shall just have to go home.’
‘Would you like me to make him quiet?’ said the flaming Spirit–an angel, as I now understood.
‘Of course I would,’ said the Ghost.
‘Then I will kill him,’ said the Angel, taking a step forward.
‘Oh–ah–look out! You’re burning me. Keep away,’ said the Ghost, retreating.
‘Don’t you want him killed?’
‘You didn’t say anything about killing him at first. I hardly meant to bother you with anything so drastic as that.’
‘It’s the only way,’ said the angel, whose burning hands were now very close to the Lizard. ‘Shall I kill it?’
‘Well, that’s a further question. I’m quite open to consider it, but it’s a new point, isn’t it? I mean, for the moment I was only thinking about silencing it because up here–well, it’s so damned embarrassing.’
‘May I kill it?’
‘Well, there’s time to discuss that later.’
‘There is no time. May I kill it?’
‘Please, I never meant to be such a nuisance. Please–really–don’t bother. Look! It’s gone to sleep of its own accord. I’m sure it’ll be all right now. Thanks ever so much.’
‘May I kill it?’
‘Honestly, I don’t think there’s the slightest necessity for that. I’m sure I shall be able to keep it in order now. I think the gradual process would be far better than killing it.’
‘The gradual process is of no use at all.’
‘Don’t you think so? Well, I’ll think over what you’ve said very carefully. I honestly will. In fact I’d let you kill it now, but as a matter of fact I’m not feeling frightfully well to-day. It would be most silly to do it now. I’d need to be in good health for the operation. Some other day, perhaps.’
‘There is no other day. All days are present now.’
‘Get back! You’re hurting me now.’
‘I never said it wouldn’t hurt you. I said it wouldn’t kill you.’
‘Oh, I know. You think I’m a coward. But it isn’t that. Really it isn’t. I say! Let me run back by to-night’s bus and get an opinion from my own doctor. I’ll come again the first moment I can.’
‘This moment contains all moments.’
‘Why are you torturing me? You are jeering at me. How can I let you tear me in pieces? If you wanted to help me, why didn’t you kill the damned thing without asking me–before I knew? It would have all been over by now if you had.’
‘I cannot kill it against your will. It is impossible. Have I your permission?’
The Angel’s hands were almost closed on the Lizard, but not quite. Then the Lizard began chattering to the Ghost so loud that even I could hear what it was saying.
‘Be careful,’ it said. ‘He can do what he says. He can kill me. One fatal word from you and he will! Then you’ll be without me for ever and ever. It’s not natural. How could you live? You’d be only a sort of ghost, not a real man as you are now. He doesn’t understand. He’s only a cold, bloodless abstract thing. It may be natural for him, but it isn’t for us. Yes, yes. I know there are no real pleasures now, only dreams. But aren’t they better than nothing? And I’ll be so good. I admit I’ve sometimes gone too far in the past, but I promise I won’t do it again. I’ll give you nothing but really nice dreams–all sweet and fresh and almost innocent. You might say, quite innocent…’
‘Have I your permission?’ said the Angel to the Ghost.
‘I know it will kill me.’
‘It won’t. But supposing it did?’
‘You’re right. It would be better to be dead than to live with this creature.’
‘Then I may?’
‘Damn and blast you! Go on, can’t you? Get it over. Do what you like,’ bellowed the Ghost: but ended, whimpering, “God help me. God help me.”
Next moment the Ghost gave a scream of agony such as I never heard on Earth. The Burning One closed his crimson grip on the reptile: twisted it, while it bit and writhed, then flung it, broken-backed, on the turf.