sit (idly) by
To stand aside and refrain from acting or intervening. They may not have broken the law themselves, but the CEOs certainly sat by and allowed these illegal activities to happen unchecked. I feel so guilty for sitting idly by while my son was going through such a difficult time in his life.
sit by someone
to sit next to someone. May I sit by you? Come over here and sit by me.
sit idly by
and stand idly byto remain close, doing nothing to help. I do not intend to stand idly by while my children need my help. The wealthy man sat idly by while the poor people starved.
sit by
Also, sit idly by. Refrain from interfering, remain passive, as in I can't just sit by and let her get in trouble.
sit by
v. To remain uninvolved; refrain from acting: I did the work while the others sat by and watched.