Cheapest priced copy (Jumpstart): $0.35 at Card Kingdom, near mint, their price list as of .
Heartfire 
Instant · Common · War of the Spark · #131
As an additional cost to cast this spell, sacrifice a creature or planeswalker.
Heartfire deals 4 damage to any target.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Jumpstart | 333 | Common | $0.35 | — |
| War of the Spark | 131 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 3 May 2019You must sacrifice exactly one creature or planeswalker to cast this spell; you can’t cast it without sacrificing one, and you can’t sacrifice additional permanents.
- 3 May 2019Players can respond to Heartfire only after it’s been cast and all its costs have been paid. No one can try to destroy the permanent you sacrificed to stop you from casting this spell.