Historical Rules · 17 November 2023
Rule 508.3a
Official source text from the 17 November 2023 Rules release
An ability that reads “Whenever [a creature] attacks, . . .” triggers if that creature is declared as an attacker. Similarly, “Whenever [a creature] attacks [a player, planeswalker, or battle], . . .” triggers if that creature is declared as an attacker attacking that player or permanent. Such abilities won’t trigger if a creature is put onto the battlefield attacking.