I know Christians often say that something always had to exist—either God, matter, energy, or even the infinitesimally small point before the Big Bang. But we don't know that at all. We don't even know that time existed before the big bang, in fact, a common theory in the scientific community is that it didn't but true to the nature of science, we haven't stopped looking (well, except people that know they have the answer already, even if they are wrong).
Or we just cop out and say "the bible says it, so that's the conclusion".