When you score a critical hit against an enemy, your deity favors you with healing or by renewing one of your prayers.

Daily   ✦     Divine, Healing
Free Action      Personal

Trigger: You roll a natural 20 when making a melee attack.

Effect: You regain hit points as if you had spent two healing surges, or you regain the use of one cleric daily attack power that you have already used today. Once you use this power, you cannot recover it except by taking an extended rest.

Published in Player's Handbook, page(s) 74, Class Compendium.