Grounding or bonding?
This is what I think you may be looking for. I may be wrong though.
250.86 Ex.#2
'05
"short sections... raceways... protection of cable assemblies from physical damage shall not be required to be connected to be grounded"
'08
"short sections... raceways... protection of cable assemblies from physical damage shall not be required to be connected to beconnected to the equipment grounding conductor"