Instill Energy

Text:

Enchant creature
Enchanted creature can attack as though it had haste.
: Untap enchanted creature. Activate only during your turn and only once each turn.

Rulings:

• 10/4/2004 If attached to an opponent’s creature, you can untap their creature during your turn.
• 10/4/2004 Instill Energy’s untap ability will not untap the creature until it resolves. This means other spells and abilities can be used before it actually becomes untapped.
• 8/1/2005 Any Auras (or other effects) which are on the creature that would cause it to not be untapped (or have a cost to be untapped) during untap step do not in any way hinder or imply a cost to use this card’s ability to untap once during the turn.