Below are a few excerpts from John Owen’s commentary about faith, from Hebrews 11:1-2 which says, “Now faith is the substance of things hoped for, the evidence of things not seen. For by it the elders obtained a good report.” (Heb 11:1-2 KJV)
“Faith is that gracious power of the mind whereby it firmly assents unto divine revelation upon the sole authority of God, the revealer, as the first essential truth, and fountain of all truth. It is unto faith that the revelation of these invisible things is made; which it mixeth and incorporates itself withal, whereby it gives an evidence unto them.
It is faith alone that takes believers out of this world whilst they are in it, that exalts them above it whilst they are under its rage; that enables them to live upon things future and invisible….
The faith of true believers from the beginning of the world was fixed on things future, hoped for, and invisible; that is, eternal life and glory in an especial manner. That was the faith whereby they ‘obtained a good report,’ as the apostle here testifies. So vain is the imagination of them who affirm that the promises under the old testament respected only things temporal; so making the whole church to have been Sadducees*. The contrary is here expressly affirmed by the apostle.
That faith whereby men please God acts itself in a fixed contemplation on things future and invisible, from whence it derives encouragement and strength to endure and abide firm in profession against all oppositions and persecutions.”
-John Owen, volume 7, Hebrews commentary
*The Sadducees did not believe in the resurrection. Without the resurrection, we have no hope of eternal life. This is what our faith is pointing us to, eternal life in and through Jesus Christ.