Giving him that rare book is like casting pearls before swine.
pearls before swine
idiomSomething of value, beauty, refinement, or wisdom left to people who will not appreciate it.
Origin
disputed originSee cast pearls before swine.
She spent hours explaining the complex symphony to her bored friends, feeling like she was casting pearls before swine.
The professor realized that offering his deepest philosophical insights to an audience only interested in gossip was merely casting pearls before swine.