Historical Rules · 18 June 2010
Rule 601.4
Official source text from the 18 June 2010 Rules release
Casting a spell that alters costs won't affect spells and abilities that are already on the stack.
Historical Rules · 18 June 2010
Official source text from the 18 June 2010 Rules release
Casting a spell that alters costs won't affect spells and abilities that are already on the stack.