Worthy Cause is a uncommon Instant card from Tempest (TMP), collector number 53. Current market price: $0.40, TCGplayer market prices via Scryfall.
Buyback {2} (You may pay an additional {2} as you cast this spell. If you do, put this card into your hand as it resolves.) As an additional cost to cast this spell, sacrifice a creature. You gain life equal to the sacrificed creature's toughness.