Enchant creature
Enchanted creature can't be blocked by creatures with power 3 or greater.
Sacrifice this Aura: The next time a source of your choice would deal damage to enchanted creature this turn, prevent that damage.
A keyword ability that defines what an Aura spell can target and what an Aura permanent can be attached to. See rule 303, “Enchantments,” and rule 702.5, “Enchant.”