To sit up

to rise from, or refrain from, a recumbent posture or from sleep; to sit with the body upright; as, to sit up late at night; also, to watch; as, to sit up with a sick person.
- Luke vii. 15.

See also: Sit

References in classic literature ?
Not only was he gambling as he had never gambled before, but he was gambling at the biggest table in the world and for stakes so large that even the case-hardened habitues of that table were compelled to sit up.
The challenge is to sit up without moving your legs at all.
But now it's time to sit up one last time and take note.