God has existed from all of eternity; nothing caused Him to exist, He had no beginning, and He will have no end.

Our only other option (from an atheist standpoint) is to believe that some sort of material / matter has eternally existed. Consequently, one must choose between an infinite personal God who has always existed or a lifeless impersonal matter.

More importantly, this question commits what scholars call a ‘category fallacy,’ it is like saying I do not believe in the musical note ‘C’ because I cannot smell (elaborated in the argument below). 

One of the best arguments I have heard on this subject was from a debate by Kent Hovind; here is a summary of what he said. 

“Asking where God came from would imply that you are thinking of the wrong God. The God of the Bible is not affected by time, space, or matter; if He had been, then He would not have been God.

To elaborate a bit more, scientists call time, space, and matter a continuum that means that they would all have to come into existence simultaneously.

If there was matter but not space, where would you put it? If there were matter and space but no time, then when would you put it? All three elements would have had to come into existence simultaneously.

The Bible clearly answers that in just ten words in the first verse of the Bible ~ Genesis 1:1.

“In the beginning (time) God created the Heavens (space) and the earth (matter).”

The God who created this universe is outside of this universe. He is above it and beyond it, in it, through it, and He is unaffected by it.

The question of where God came from assumes that there is a limited God, which is our biggest problem. The God of the Bible is not limited by time, space, or matter. 

If we could fit the infinite God in our three-pound brain, then He would not be worth worshiping. 

We must not limit the infinite God by our finite understanding.

Psalm 90:2 (NKJV)

Before the mountains were brought forth, Or ever You had formed the earth and the world, Even from everlasting to everlasting, You are God.