Tides of Knowledge

Choose a player. That player may choose to exile a nonland card from their hand face down. For as long as that card remains exiled, you may look at it, you may cast it, and you may spend mana as though it were mana of any type to cast it. Draw two cards.
When you cast the exiled card, exile a nonland card from your hand face down. For as long as that card remains exiled, the initially chosen player may look at it, they may cast it, and they may spend mana as though it were mana of any type to cast it.