■Holy two-piece Increases the healing done by your Daybreak ability by 50%.
■Holy four-piece Increases the healing transferred to your Beacon of Light target by 20%.
■Protection two-piece Casting Word of Glory or Eternal Flame also grants you 40%
additional block chance for 5 sec per Holy Power.
■Protection four-piece You gain 1 Holy Power for each % of your health taken as damage while Divine Protection is active.
■Retribution two-piece Your Exorcism causes your target to take 6% increased Holy damage from your attacks for 6 sec.
■Retribution four-piece Your Crusader Strike has a 40% chance to make your next Templar's Verdict deal all Holy damage.
found at: http://wow.joystiq.com/2013/01/10/tier-15-set-bonuses-unveiled-in-latest-ptr-patch/