When reduced below 30% health, you gain the Sacred Shield effect. The Sacred Shield absorbs ((1) + (AP * 2.8)) damage and increases healing received by 20%. Lasts 15 sec. This effect cannot occur more than once every 60 sec.
When reduced below 30% health, you gain the Sacred Shield effect. The Sacred Shield absorbs ((1) + (AP * 2.8)) damage and increases healing received by 20%. Lasts 15 sec. This effect cannot occur more than once every 60 sec.
Since patch 3.2, Sacred Shield CAN NOT stack several times on a single target.
If the Divine Guardian talent is used, the duration of Sacred Shield buff will increase to 9/12 seconds while the buff will still be able to refresh every 6 seconds.
The Sacred Shield receives approximately 25% of the casting Paladin's spell power.
Damage over time effects will proc the Sacred Shield buff.
An important note for ret Paladins is that casting Sacred Shield resets weapon swing timer.
Environmental damage (e.g. fall damage, lava) is not absorbed.
[Stoicism] reduces the chance that your spells will be dispelled by an additional 10/20/30%.
[Divine Guardian] increases the duration of Sacred Shield by 50/100% and the amount absorbed by 10/20%. This includes the increase of duration in both the main Sacred Shield buff, to 45/60 seconds, and the damage absorbing buff, to 9/12 seconds. The Sacred Shield will still be able to proc every 6 seconds.
Damage over time effects trigger the Shield's buff making this ability very useful in pvp combat. It is a viable tactic to intentionally suffer a less harmful DoT spell on yourself in order to have it constantly proc the Sacred Shield buff.
Ret Paladins should time their The Art of War instant Flash of Light casts with the buff from the Sacred Shield.
Paired with Illumination and Beacon of Light talents, the additional 50% Flash of Light crit chance will greatly increase the mana effectiveness of Paladin's healing. Thus, holy Paladin's main target should be protected by the Sacred Shield buff whenever possible.
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."
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.
Edit
[Infusion of Light] causes your Flash of Light to heal targets with Sacred Shield for an additional 50/100% over 12 sec.
[Stoicism] reduces the chance that your spells will be dispelled by an additional 10/20/30%.
[Divine Guardian] increases the duration of Sacred Shield by 50/100% and the amount absorbed by 10/20%. This includes the increase of duration in both the main Sacred Shield buff, to 45/60 seconds, and the damage absorbing buff, to 9/12 seconds. The Sacred Shield will still be able to proc every 6 seconds.
[Benediction] reduces the mana cost of instant spells by 1/2/3/4/5%.
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 (2009-08-04):
