Need quick answer: rear hub motor wire should exit facing up or down?

I'm installing my rear wheel and I'm not sure which way is safer or recommended.
The axle thread has a slit in it which I can orient up or down to let the motor wire curve and exit in that direction.
In terms of safety/waterproofing/etc, which way should I curve the wire, up or down?

It should absolutely be mounted so the cable points down, and then curves back up to be zip-tied to the frame. Doing this is called a "drip loop".

Its impossible to avoid keeping humidity out of the inside of the motor, but the heat of the motor evaporates almost all of it on a regular basis. If the cable is pointing up, ant water that splashes onto it will run down the cable into the interior of the motor. If it is raining, you would be guaranteed to get an entire cups worth of water into the motor every time you ride...

Ok, thanks a lot for the quick informative answer!