Look a Gift Horse in the Mouth

There's a old-timey phrase that goes - Why he'd look a gift horse in the mouth. It comes from back when people used horses for pulling plows and the like. Back then the buyer would look in the horse's mouth to determine how healthy and therefore how good the horse was. Well, if someone is giving you a horse, would you look in its mouth to see if you wanted to take it? That's the point, your not supposed to be so ungrateful that you'd do such a thing.

Well, we've done it. The US turned back some food rations provided by the German military, because we are afraid that they might be infested with Mad Cow Disease.