Wikia

Serendipity
Serendipity (Passive) Passive When you heal with Binding Heal or Flash Heal, the cast time of your next Greater Heal or Prayer of Healing spell is reduced by 20% and mana cost reduced by 10%. Stacks up to 2 times. Lasts 20 sec.
Usable by
Class	Priest
Properties
Type	Utility
School	Physical
Talents
Specialization	Holy
Level required	34
Related buff
Magic Serendipity Reduces the cast time of your next Greater Heal or Prayer of Healing by 20% and mana cost by 10%. Duration: 20 seconds

Serendipity is a passive priest ability learned at level 34 for those with the Holy specialization. It reduces the cast time of your next [Greater Heal] or [Prayer of Healing] whenever you cast [Binding Heal] or [Flash Heal].

Trivia

Patch 4.0.6 (8-Feb-2011): Serendipity now has Spell Alert and Floating Combat Text feedback support.
Hotfix (2009-04-23): "The Priest ability Serendipity is now properly consumed when a spell finishes casting and does not affect a second spell. ^[1]"
Patch 3.1.0 (14-Apr-2009): Re-designed: When you heal with Binding Heal or Flash Heal, the cast time of your next Greater Heal or Prayer of Healing spell is reduced by 6/12/20%. Stacks up to 3 times. Lasts 20 sec.
/ Patch 3.0.2 (14-Oct-2008): Added.