When people speak of faith or belief in God, they are almost always referring to belief in God’s existence. “Do you believe in God?” means “Do you believe God exists?”
The existence of God is never a question in the Bible. After all, whose Word is it? Biblical faith is not a belief in God’s existence. Biblical faith is a belief that God will keep his promises. Throughout the Bible, God’s existence is a given. Faith refers to a belief that God will do as He promises.
Adapted from Genesis, The Rational Bible, Prager