Flare of Fortitude is a rare Instant card from Modern Horizons 3 Promos (PMH3), collector number 26s. Current market price: — (foil $9.85), TCGplayer market prices via Scryfall.
You may sacrifice a nontoken white creature rather than pay this spell's mana cost. Until end of turn, your life total can't change, and permanents you control gain hexproof and indestructible.