Cast Down 
Feat 6ClericConcentrateMetamagicSource Core Rulebook pg. 123 2.0Prerequisites harmful font or healing font
The sheer force of your faith can bring a foe crashing down. If the next action you use is to cast
harm or
heal to damage one creature, the target is knocked prone if it takes any damage from the spell. If the target critically fails its save against the spell, it also takes a –10-foot status penalty to its Speed for 1 minute.
Traits
Concentrate: An action with this trait requires a degree of mental concentration and discipline.
Metamagic: Actions with the metamagic trait, usually from metamagic feats, tweak the properties of your spells. You must use a metamagic action directly before Casting the Spell you want to alter. If you use any action (including free actions and reactions) other than Cast a Spell directly after, you waste the benefits of the metamagic action. Any additional effects added by a metamagic action are part of the spell’s effect, not of the metamagic action itself.