One common formulation of the cosmological argument begins, "everything that exists requires a cause." (example) Smart people sometimes formulate the argument this way, but it is actually not correct.
A better (let's call it "the correct") formulation is, "Everything that comes into existence has a cause."
Under the incorrect formulation you either have contradiction or infinite regress.
Under the correct formulation you have a singularity. A first cause who is uncaused. As a result, that uncaused cause must never have come into being: he must always have been. This is because if that cause had come into existence, there would have to be a still earlier cause. On the other hand, if that cause did not exist at all, and consequently never came into existence in that sense, nothing could exist.
This causeless first Cause, without whom nothing would exist, is God.