From The Lord of the Rings by J.R.R. Tolkien, specifically the chapter The Shadow of the Past, in which Gandalf responds to Frodo’s statement that Gollum is an enemy who deserves death:
Deserves it? I daresay he does. Many that live deserve death. And some that die deserve life. Can you give it to them? Then do not be too eager to deal out death in judgment. For even the wise cannot see all ends. I have not much hope that Gollum can be cured before he dies, but there is a chance of it.
I sometimes wonder if reading that quote as a youth was a seed that ultimately lead to my changing my mind about supporting the death penalty many years later. Obviously, it’s not the only reason, but I’ve remembered it ever since I was a teenager, and it’s a quote that still resonates with me today.