I am redoing a ceiling fan with new wiring. I have the walls open at the switch box. There is an old knob & tube hot wire coming in and then it goes out to the ceiling fan. I have run new wiring to the ceiling fan and have put an outlet right below where the new plastic box is going for the switch. I can't find where the feed is for the hot wire, it is somewhere in the ceiling. I have gone to the other fixtures that are on the same breaker and don't see the hot wire being fed from there. What do I do with this?
You must terminate the wire in a box and it must remain accessible with a cover plate. You need to terminate it with the appropriately sized wire nut.
This may help locate the hidden splice: get a voltage sensor ($5), turn off all breakers except for this one. Put the sensor on high sensitivity and start sweeping around on the ceiling. You might get lucky and find a hidden box or at least you'll get to know how the wires are run and get a better feel for which switch or light box contains the feed.