Be kind. Don't kill for any reason. Don't even kill out of self-defense. Really — I mean that. Don't take any more than you need of anything. Help others.
Source, in full
From a speech given on 20 January 1969 at the University of Michigan, about two months before Slaughterhouse Five was published, as reported in "A very new kind of WIR [Writer in Residence]" by Daniel Okrent, feature editor, The Michigan Daily (21 January 1969), pp. 1–2