“He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; and being fully persuaded that, what he had promised, he was able also to perform.” (Romans 4:9-24)
Abraham’s faith, which is what this verse is discussing, was based upon “that which was spoken“. (vs. 18) This has always been the basis of true faith. Believing what God has spoken.
In our case today, true faith is based upon that which God has written. What He has inspired or breathed out.
True faith is based upon every word of God.