Gustrider Exuberant — ruling 1

The ability doesn’t target, so it checks the creatures’ powers only once: when the ability resolves. Once the ability resolves, it will continue to apply to the affected creatures no matter what their powers may become later in the turn.

Gustrider Exuberant : règles, fonctionnement et interactions (MTG)

Gustrider Exuberant 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

Flying Sacrifice this creature: Creatures you control with power 5 or greater gain flying until end of turn.

How it works : Gustrider Exuberant

Original English text — Wizards of the Coast / Scryfall

#1October 1, 2008· Wizards of the Coast
The ability doesn’t target, so it checks the creatures’ powers only once: when the ability resolves. Once the ability resolves, it will continue to apply to the affected creatures no matter what their powers may become later in the turn.
No other card is named in this ruling.