He is the foundation for faith. He is the basis for faith. Our faith rests upon the reliability of God, not upon the changing feelings of the human heart. We only put our faith in God's Word because of God. Faith in God's Word is faith in God, who stands behind His Word.
Human words are unreliable.
This is because humans are unreliable. God's Word, on the other hand, is reliable because God stands behind it. It is His Word. It has authority because He is the ultimate authority in the Universe. Therefore, when we choose to believe God's Word, we are choosing to believe in the God who stands behind His Word.