Source, in full
Attributed to Sun Tzu in multiple books and internet sites, but this text does not appear in The Art of War and seems to be a more recent creation is very possible that is came from an anime that miscredited this saying Sun Tzu.
More quotes by Sun Tzu
Secret operations are essential in war; upon them the army relies to make its every move.
Management of many is the same as management of few. It is a matter of organization.
Attribution
Quote text and notes from Wikiquote: Sun Tzu (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.