Historical Rules · 23 July 2021
Rule 601.2a
Official source text from the 23 July 2021 Rules release
To propose the casting of a spell, a player first moves that card (or that copy of a card) from where it is to the stack. It becomes the topmost object on the stack. It has all the characteristics of the card (or the copy of a card) associated with it, and that player becomes its controller. The spell remains on the stack until it resolves, it’s countered, or a rule or effect moves it elsewhere.