The Sheep-Biter and Shepherd
A certain Shepherd had a Dog, upon whose fidelity he relied very much; for whenever he had occasion to be absent himself, he committed the care and tuition of the flock to the charge of his Dog; and, to encourage him to do his duty cheerfully, he fed him constantly with sweet curds and whey, and sometimes threw him a crust or two. Yet, notwithstanding this, no sooner was his back turned, but the treacherous cur fell foul of the flock, and devoured the sheep, instead of guarding and defending them. The Shepherd being informed of this, was resolved to hang him; and the Dog, when the rope was about his neck, and he was just going to be hung, began to expostulate with his master, asking him, why he was so unmercifully bent against him, who was his own servant and creature, and had only committed two or three crimes, and why he did not rather execute vengeance upon the Wolf, who was a constant and declared enemy? "Nay," replies the Shepherd, "it is for that very reason that I think you ten times more deserving of death than he. From him I expected nothing but hostilities; and therefore could guard against him. You I depended upon as a just and faithful servant, and fed and encouraged you accordingly; and therefore your treachery is the more notorious, and your ingratitude the more unpardonable."
A known enemy is better than a treacherous friend.