Rethink

Instant    (CMC:3)

Counter target spell unless its controller pays , where X is its converted mana cost.

"Are you sure you want to do that?"

42 PR • ENMatt Cavotta

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Legal in: Masques Block,Legacy,Vintage,Commander

Oracle Text (click to copy):

10/4/2004
The spell's controller gets the option to pay when this spell resolves.