Change of Heart
Instant
Buyback 
(You may pay an additional as you cast this spell. If you do, put this card into your hand as it resolves.)
Target creature can't attack this turn.
Ron Spencer
Stronghold (STH)
• #3Rulings
Change of Heart will not remove an already attacking creature from combat. It must be cast before attackers are declared or it won’t have any noticeable effect on the game.
(wotc • 2004-10-04)
Rulings
Change of Heart will not remove an already attacking creature from combat. It must be cast before attackers are declared or it won’t have any noticeable effect on the game.
(wotc • 2004-10-04)