No, it's still plagerism. Either way, if you take credit for someone else's work it's considered plagerism. People have got into trouble over it for giving speeches that consisted of large sections of other's work (not the least of whom Martin Luther King, jr.).
With one liners like that, especially once they've become part of common speech I don't think it's plagerism in print or speech. I mean, I don't know off the top of my head who originally said that the first casualty of war is truth, but it's so often repeated that it's not really necessary to cite a source.
and so on