Is it safe to drink reboiled water?
Reboiling water will do precisely three things:


Some volatile contaminants in the water that survived the first boiling might be driven out by the second boiling.
Some additional evaporation will occur, causing anything dissolved in the water (salts, contaminants) to be slightly more concentrated.
Some additional material from the surface of the vessel you're boiling the water in might dissolve into the water.


It's virtually impossible to imagine any scenario in which this would matter, unless you were taking a huge amount of barely drinkable water and boiling away most of it or using a vessel whose lining could produce toxins in your water. Needless to say, you really shouldn't be drinking barely drinkable water at all, nor should you be boiling water even once in a vessel whose lining can produce toxins. If you're doing these kinds of things, the additional risk from reboiling would be miniscule.

It will definitely not summon aresenic or lead from nowhere.