stay stillUsed to tell someone or something to remain motionless or stay put. It can also mean to stay quietly in one place, as in staying at home. Forms such as じっとしてて and じっとしてろ are informal commands.
stay stillUsed to tell someone not to move or fidget. It can be softened as じっとしていて or made more casual and forceful with forms such as じっとしてな and じっとしてるんだぞ.