Mere Christianity, in The Complete C. S. Lewis Signature Classics

p. 47

“Christianity asserts that every individual human being is going to live forever . . . There are a good many things that would not be worth bothering about if I were going to live only seventy years, but which I had better bother about very seriously if I am going to live forever.  Perhaps my bad temper or my jealousy are gradually getting worse—so gradually that the increase in seventy years will not be very noticeable.  But it might be absolute hell in a million years: in fact, if Christianity is true, Hell is the precisely correct technical term for what it would be.”