|dog in the manger|
|a. a person who prevents others from using something he has no use for|
|b. (as modifier): a dog-in-the-manger attitude|
A person who spitefully refuses to let someone else benefit from something for which he or she has no personal use: “We asked our neighbor for the fence posts he had left over, but, like a dog in the manger, he threw them out rather than give them to us.” The phrase comes from one of Aesop's fables, about a dog lying in a manger full of hay. When an ox tries to eat some hay, the dog bites him, despite the fact that the hay is of no use to the dog.