Blessing of Sanctuary has been removed and is now just called Sanctuary. It is a passive buff to the Protection Paladin in the third tier of the Protection tree. A player can invest three points into it, with the final result being: "Reduces the chance that you will be critically hit by melee attacks by 6% and reduces all damage taken by 10%. Also whenever you block or dodge a melee attack you gain 3% maximum mana."
This section concerns content exclusive to Cataclysm.
Blessing of Sanctuary becomes a passive effect for the paladin instead of a buff in Cataclysm.
Blessing Sanctuary was renamed Sanctuary, is now passive and ranks up to three times.
Patch 3.2.2 (2009-09-22): This blessing now grants 10% strength in addition to its current effects. Also, the strength and stamina bonuses from this blessing will no longer be lost when Blessing of Kings is removed.
This blessing now also increases stamina by 10%. This effect is cumulative with [Blessing of Kings].
This talent and [Vigilance] will now both be able to be cast on the same target without sometimes overwriting each other. "...we want to make sure Blessing of Sanctuary is always the tanking blessing of choice" (source)
Patch 3.1.0 (14-Apr-2009): Now only grants mana on dodge/parry/block. In addition, will only grant mana if that is the active power type of the friendly target (Bears and Cats won't gain mana). Old, gain 10 rage , 20 runic power, or 2% of the maximum mana
/Patch 3.0.2 (14-Oct-2008): Reduced to 1 rank, now reduces all damage taken by 3% and generates rage, mana or runic power when a parry/dodge/block occurs. Old, 5 ranks. Last rank text was "Places a Blessing on the friendly target, reducing damage dealt from all sources by up to 80 for 10 min. In addition, when the target blocks a melee attack the attacker will take 46 Holy damage."