Scattering Stroke (Commander 2011 60) - Uncommon Magic: The Gathering Card

Counter target spell. Clash with an opponent. If you win, at the beginning of your next main phase, you may add an amount of equal to that spell's mana value. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)