Historical Rules · 29 September 2017
Rule 115.2f
Official source text from the 29 September 2017 Rules release
A player who has a card with suspend in his or her hand may exile that card. This is a special action. A player can take this action any time he or she has priority, but only if he or she could begin to cast that card by putting it onto the stack. See rule 702.61, “Suspend.”