Patch 4.1.0 (26-Apr-2011): Sacred Shield's internal cooldown has been increased to 60 seconds, up from 30.
Patch 4.0.6 (8-Feb-2011): New version added, replacing Rebuke; When reduced below 30% health, paladins gain the Sacred Shield effect. The Sacred Shield absorbs X damage and increases healing received by 20%. Lasts 15 seconds. This effect cannot occur more than once every 30 seconds. Undispellable.
Hotfix (2010-02-05): "The amount of damage being absorbed by Sacred Shield and Power Word: Shield is being reduced by 10% correctly in only battlegrounds, Arenas, and Wintergrasp."
Patch 3.2.0 (04-Aug-2009): This buff will no longer have any effect if the target is another player engaged in a duel. In addition, the heal from this buff will no longer cause the paladin to stand, and it is no longer possible for two paladins to both have the spell active on one target. When a paladin casts Flash of Light on a target with this buff, they also now place a heal over time effect on the target, healing that target for 100% of the Flash of Light amount over 12 seconds. This only applies if the paladin has Infusion of Light.
Patch 3.1.0 (14-Apr-2009): This effect cannot be cast on more than one friendly target at a time. Now scales properly from spell power granted by Sheath of Light.