I don't believe 300.3(B)(3) would include the words cable and cords if it only applied to individual conductors. NM and plastic boxes would comply with 300.20(B) because it says where, and since we don't have any "where" single conductors pass through ferrous metals, we are by default already in compliance.

Where is the light fixture in this scheme? How is the second switch wired? Where is the incoming power wired in? Is this the end of the branch circuit or does the power feed through to other devices? Might it be a four-way setup? There are several variations on how to connect a three-way light so you need to know how the other elements are connected. I recommend that you study a book on basic residential wiring. There should be several at your local library or you can find them at home Depot, Lowes, etal. Your web browser should also be able to find a few illustrated explanations.

jagmtx- That's good to hear! And I apologize if my reply was offensive. Most likely the two connections on the left hand side of the picture are the switched hot and neutral but that would have to verified with a volt meter first - you can never assume. The bare copper on the right is your ground. As far as the fan, standard color coding would indicate the green is your ground, white is neutral, black is the hot for the fan, and the black/white (although it's usually Blue) should the hot for the light. Again, I would double check that with a meter. Once things are confirmed make sure the power is off at the breaker before installing - you never know what the last position the fan switch (on the fixture) was left in!

From the 2nd switch you only need two conductors, a hot and a neutral, going to the light. The hot will come from the "common" terminal on the switch. No reason to replace the cable, just leave the 3rd wire disconnected. Whomever wired it to begin with probably either had extra 14/3 around, or wanted flexibility, for example to power a fan and a light separately.