Stay the Hand

Enchantment (Compulsion) [mind-affecting]
Level: Paladin * 4
Components: V, S, DF
Casting Time: 1 Immediate Action
Range: medium (100 ft. + 10 ft./level)
Target: one creature
Duration: 1/round per level and special; see text
Saving Throw: Will partial
Spell Resistance: yes
  You cause a creature's arm to waver and prevent it from striking another creature. You can cast this spell when the target is about to make a Melee Attack against another creature. On a failed saving throw, the target does not follow through with its attack, and its entire action is wasted for the round. On a successful saving throw, the target can make its attack, forcing its strike though the Compulsion but losing both accuracy and power, taking a -5 penalty on its attack and damage rolls. Whether or not the target makes its initial save or not, it is subject to a -2 penalty on attack and damage rolls against the creature it originally targeted for the duration of the spell.