Fig.. to do nothing; to take no action in a problematic situation

Are you going to help your mother or are you just going to sit there on your hands and watch her while she's working for you?

Aiuterai tua madre o te ne starai lì con le mani in mano a guardarla mentre lavora per te?

It's been proved that this easily preventable tragedy happened because the authorities decided to sit on their hands and do nothing

È stato provato che questa tragedia, facilmente evitabile, è accaduta perché le autorità se ne sono state con le mani in mano e hanno deciso di non fare niente

While you were off, we worked on the project anyway because we are so far behind that we cannot afford sitting on our hands

Mentre non c'eri abbiamo comunque portato avanti il progetto perché siamo talmente in ritardo che non possiamo permetterci il lusso di starcene con le mani in mano

The expression comes from the world of theater, in fact the original meaning of the idiom was "to fail to applaud". If the people in the audience choose to keep their hands warm by sitting on them, there would be no applause!