Halo of Peace is a 17th level cleric Encounter prayer that was introduced in Divine Power.
Halo of Peace
Cleric Attack 17
You slam your weapon into your foe and enfold it in brilliant energy that hampers its attacks.
Melee weapon
Target: One creature
Attack: Strength vs. AC
Hit: 2[W] + Strength modifier radiant damage. Until the end of your next turn, the target takes a -4 penalty to attack rolls and cannot make opportunity attacks.