Bayou Groff — ruling 1

You must sacrifice exactly one creature or pay an extra {3} to cast this spell; you can’t cast it without paying one of those costs, and you can’t pay either multiple times.

Bayou Groff — ruling 2

Players can respond to Bayou Groff only after it’s been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to stop you from casting this spell or to make it cost more mana.

Bayou Groff : règles, fonctionnement et interactions (MTG)

Bayou Groff is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

As an additional cost to cast this spell, sacrifice a creature or pay .

How it works : Bayou Groff

Original English text — Wizards of the Coast / Scryfall

#1April 16, 2021· Wizards of the Coast
You must sacrifice exactly one creature or pay an extra to cast this spell; you can’t cast it without paying one of those costs, and you can’t pay either multiple times.
No other card is named in this ruling.
#2April 16, 2021· Wizards of the Coast
Players can respond to Bayou Groff only after it’s been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to stop you from casting this spell or to make it cost more mana.
No other card is named in this ruling.