Standstill
Enchantment
When a player casts a spell, sacrifice this enchantment. If you do, each of that player's opponents draws three cards.
"Take your time."
Heather Hudson
Odyssey (ODY)
• #102Rulings
It only works once. If someone casts another spell after it triggers, but before that trigger resolves, then it will trigger again. The first time one of these triggers resolves, it will be sacrificed for the full effect. Any additional triggers on the stack will do nothing when they resolve because you will be unable to sacrifice it additional times.
(wotc • 2004-10-04)
Rulings
It only works once. If someone casts another spell after it triggers, but before that trigger resolves, then it will trigger again. The first time one of these triggers resolves, it will be sacrificed for the full effect. Any additional triggers on the stack will do nothing when they resolve because you will be unable to sacrifice it additional times.
(wotc • 2004-10-04)