What does the phrase “to nourish a snake in one’s bosom” mean and Where does it come from?

The saying “to nourish a snake in one’s bosom” takes us again to our old Greek friend, Aesop.

The available translation tells this story under the title, “The Farmer and the Snake”:

“A Farmer found in the winter a Snake stiff and frozen with cold. He had compassion on it, and taking it up placed it in his bosom. The Snake on being thawed by the warmth quickly revived, when, resuming his natural instincts, he bit his benefactor, inflicting on him a mortal wound. The Farmer said with his latest breath, ‘I am rightly served for pitying a scoundrel.’ Moral: The greatest benefits will not bind the ungrateful.”