Historical Rules · 8 July 2017
Rule 506.6
Official source text from the 8 July 2017 Rules release
Some spells state that they may be cast “only [before/after] [a particular point in the combat phase],” in which that point may be “attackers are declared,” “blockers are declared,” “the combat damage step,” “the end of combat step,” “the combat phase,” or “combat.”