Illumination

From wow.incgamers.com

Talent: Illumination
Effect: After getting a critical effect from your Flash of Light, Holy Light, or Holy Shock heal spell, gives you a chance to gain Mana equal to 60% of the Base Cost of the spell.
Statistics: Rank 1 = 20% chance, Rank 2 = 40%, Rank 3 = 60%, Rank 4 = 80%, Rank 5 = 100%.