The Self-Existence of God

”God has no origin,” said Novatian, and it is precisely this concept of no-origin which distinguishes That-which-is-God from whatever is not God.
Origin is a word that can apply only to things created. When we think of anything that has origin we are not thinking of God. God is self-existent, while all created things necessarily originated somewhere at some time. Aside from God, nothing is self-caused.

(A.W. Tozer, The Knowledge of the Holy: The Attributes of God (Their Meaning in the Christian Life), New York: Harper & Row, Publishers, 1975, 32)