Cunning Rhetoric is a rare Enchantment card from Commander Masters (CMM), collector number 864. Current market price: $3.66, TCGplayer market prices via Scryfall.
Whenever an opponent attacks you and/or one or more planeswalkers you control, exile the top card of that player's library. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast it.