sit up with

sit up with someone

to stay with someone through the night, especially with a sick or troubled person or with someone who is waiting for something. I had to sit up with my younger sister when she was ill. I sat up with Bill while he waited for an overseas telephone call.
See also: sit, up
References in classic literature ?
He'll make Ward sit up with a show of local talent that'll make the rest of you sit up.
Bend your knees and sit up with your hands behind your head.