Cheapest priced copy (Magic 2012): $2.49 at Card Kingdom, near mint, their price list as of .
Guardians' Pledge 
Instant · Common · Magic 2012 · #22
White creatures you control get +2/+2 until end of turn.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $2.49 to $17.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic 2012 | 22 | Common | $2.49 | $17.99 |
2 rulings from Wizards of the Coast
- 22 September 2011Guardians' Pledge only gives a bonus to white creatures you control when it resolves. Creatures that enter later in the turn and nonwhite creatures that become white later in the turn will not get the bonus.
- 22 September 2011If a white creature that gets the bonus stops being white later in the turn, it will continue to get +2/+2 until end of turn.