Brainwash
Enchantment — Aura
Enchant creature
Enchanted creature can't attack unless its controller pays 
.
"They're not your friends; they despise you. I'm the only one you can count on. Trust me."
Pete Venters
The Dark (DRK)
• #3Rulings
Paying this cost is not an instant or any other kind of ability, it is an additional cost on the declaration of the attacker.
(wotc • 2004-10-04)
This ability is paid for during the declare attackers step of the combat phase.
(wotc • 2004-10-04)
If there are multiple combat phases during the turn, the attack cost must be paid each time if you want to attack with the creature.
(wotc • 2004-10-04)
Rulings
Paying this cost is not an instant or any other kind of ability, it is an additional cost on the declaration of the attacker.
(wotc • 2004-10-04)
This ability is paid for during the declare attackers step of the combat phase.
(wotc • 2004-10-04)
If there are multiple combat phases during the turn, the attack cost must be paid each time if you want to attack with the creature.
(wotc • 2004-10-04)