It's at the beginning of Eclipse. Anyways, here it is.
FIRE AND ICE
Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.
Ta-da. Well, there you go