Your holy power burns the undead like fire.
Benefit(s): When you use your Turn Undead feat, undead failing their saving throw are engulfed in holy fire. This functions identically to catching on fire, but the damage dealt is divine (like the divine damage from flame strike) rather than fire. Water cannot extinguish this holy fire, but any negative energy effect that heals the creature of at least 5 points of damage extinguishes the flames instantly.
Pathfinder Player Companion: Cohorts and Companions © 2015, Paizo Inc.; Authors: Brian Duckwitz, Philip Minchin, and Jason Nelson.