Furnace Celebration
Enchantment
Whenever you sacrifice another permanent, you may pay 
. If you do, this enchantment deals 2 damage to any target.
Nothing impresses goblins more than something that's bound to kill them.
Svetlin Velinov
Commander 2013 (C13)
• #109Rulings
You can't pay {2} more than once each time Furnace Celebration's ability resolves.
(wotc • 2020-11-10)
You choose whether to pay {2} as the ability resolves, if that target is still legal. No player may take actions between the time you pay {2} and the time damage is dealt.
(wotc • 2020-11-10)
Furnace Celebration itself doesn't allow you to sacrifice any permanents. Its ability triggers whenever you sacrifice a permanent because something else instructed you to.
(wotc • 2020-11-10)
Rulings
You can't pay {2} more than once each time Furnace Celebration's ability resolves.
(wotc • 2020-11-10)
You choose whether to pay {2} as the ability resolves, if that target is still legal. No player may take actions between the time you pay {2} and the time damage is dealt.
(wotc • 2020-11-10)
Furnace Celebration itself doesn't allow you to sacrifice any permanents. Its ability triggers whenever you sacrifice a permanent because something else instructed you to.
(wotc • 2020-11-10)