Which is another way of saying where did the mass come from? They are equivalent. Energy and mass are simply waves of nothing.
If you take it one step further to QM you will see the answer in the spontaneous pair production. In the final equation it all balances out.
The big bang, expansion of the universe, energy, matter, etc. Can all be explained from the particle anti particle spontaneous creation that occurs all the time. The energy balance stays the same though, zero. : ) Something really does come from nothing and it will go back to nothing too.
So the Bible really is right. Imagine that....
Ah...
FAITH!