Cheapest priced copy (Duel Decks: Heroes vs. Monsters): $0.35 at Card Kingdom, near mint, their price list as of .
Bonds of Faith 
Enchantment — Aura · Common · Duel Decks: Heroes vs. Monsters · #24
Enchant creature
Enchanted creature gets +2/+2 as long as it's a Human. Otherwise, it can't attack or block.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
4 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Heroes vs. Monsters | 24 | Common | $0.35 | — |
| Duel Decks: Blessed vs. Cursed | 2 | Common | $0.35 | — |
| Innistrad | 5 | Common | $0.35 | $0.49 |
| The List | DDQ-2 | Common | $0.35 | — |
One ruling from Wizards of the Coast
- 22 September 2011Once the enchanted creature has been declared as an attacking or blocking creature, causing it to stop being a Human won’t remove it from combat. It will lose the +2/+2 bonus, however.