Old Man Willow — ruling 1

You don't choose a target for Old Man Willow's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you sacrifice a creature or token this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.

Old Man Willow : règles, fonctionnement et interactions (MTG)

Old Man Willow 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

Old Man Willow's power and toughness are each equal to the number of lands you control. Whenever Old Man Willow attacks, you may sacrifice another creature or a token. When you do, target creature an opponent controls gets -2/-2 until end of turn.

How it works : Old Man Willow

Original English text — Wizards of the Coast / Scryfall

#1June 16, 2023· Wizards of the Coast
You don't choose a target for Old Man Willow's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you sacrifice a creature or token this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.
No other card is named in this ruling.