Divine Warrior

 
Prerequisite(s): Ability to Turn/Rebuke Undead, proficiency in Deities favored weapon, BAB 6+.
 
Benefit: Spend a turn/rebuke attempt as a swift action to temporarily grant your held weapon (which must be your deities favored weapon), either the Holy or Unholy property. This effect applies only to the next attack you make with the weapon: if you do not attack before the start of your next turn, the effect fades.
 
If you normally turn undead, this feat grants your weapon the holy property. If you normally rebuke undead your weapon gains the unholy property. This effect overrides any alignment or similar property that the weapon normally has.
 
Source: Faiths of Eberron