The snake story to which you refer -
There once was a tender-hearted woman who rescued a poor, half-frozen snake from near death in the winter cold. “Take me in, oh tender woman,” the snake cries out. “Take me in, for heaven’s sake.” So the tender-hearted woman takes the snake into her own home, warms it by the fire and feeds it milk and honey: “If I hadn’t brought you in, by now you might have died.” But instead of saying thanks, the snake gave her a vicious bite. “I saved you,” cried the woman. “And you’ve bitten me, but why? You know your bite is poisonous, and now I’m going to die.” “Oh shut up, silly woman,” said the reptile with a grin. “You knew damn well I was a snake before you took me in.”