Cheapest priced copy (Amonkhet): $0.35 at Card Kingdom, near mint, their price list as of .
Protection of the Hekma 
Enchantment · Uncommon · Amonkhet · #23
If a source an opponent controls would deal damage to you, prevent 1 of that damage.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Amonkhet | 23 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 18 April 2017If multiple sources would deal damage to you at once (for example, several attacking creatures), 1 damage from each of those sources is prevented.
- 18 April 2017Damage that would be dealt to creatures you control is unaffected.