Enchantment, 2U (3) Whenever an opponent plays a spell, you may draw a card unless that player pays {1}. Friends teach what you want to know. Enemies teach what you need to know.
Illus. Terese Nielsen
The player gets the option to pay when this triggered ability resolves. [Prophecy FAQ 2000/05/25] This will be after the spell is announced, but before it resolves. [DeLaney 2000/06/20]
You don't have to decide whether or not you are drawing until after the player decides whether or not to pay. [DeLaney 2000/05/29]