Burn the Impure is a common Instant card from Mirrodin Besieged (MBS), collector number 59. Current market price: $0.03 (foil $0.40), TCGplayer market prices via Scryfall.
Burn the Impure deals 3 damage to target creature. If that creature has infect, Burn the Impure deals 3 damage to that creature's controller.