Historical Rules · 1 October 2009
Rule 405.4
Official source text from the 1 October 2009 Rules release
Each spell has all the characteristics of the card associated with it. Each activated or triggered ability that's on the stack has the text of the ability that created it and no other characteristics. The controller of a spell is the person who cast the spell. The controller of an activated ability is the player who activated the ability. The controller of a triggered ability is the player who controlled the ability's source when it triggered, unless it's a delayed triggered ability. The controller of a delayed triggered ability is the player who controlled the spell or ability that created it.