Historical Rules · 25 January 2019
Rule 702.54a
Official source text from the 25 January 2019 Rules release
Haunt is a triggered ability. "Haunt" on a permanent means "When this permanent is put into a graveyard from the battlefield, exile it haunting target creature." "Haunt" on an instant or sorcery spell means "When this spell is put into a graveyard during its resolution, exile it haunting target creature."