Bold Defense is a common Instant card from Zendikar (ZEN), collector number 3. Current market price: $0.10 (foil $0.10), TCGplayer market prices via Scryfall.
Kicker {3}{W} (You may pay an additional {3}{W} as you cast this spell.) Creatures you control get +1/+1 until end of turn. If this spell was kicked, instead creatures you control get +2/+2 and gain first strike until end of turn.