Historical Rules · 7 June 2024
Rule 701.10a
Official source text from the 7 June 2024 Rules release
A spell or ability may instruct players to exchange something (for example, life totals or control of two permanents) as part of its resolution. When such a spell or ability resolves, if the entire exchange can’t be completed, no part of the exchange occurs. Example: If a spell attempts to exchange control of two target creatures but one of those creatures is destroyed before the spell resolves, the spell does nothing to the other creature.