Do you lack faith? The great nineteenth century English preacher, C. H. Spurgeon, described it this way:
Knowledge comes first. Drink deep of the doctrine that Christ died in our behalf; for therein lies the sweetest possible comfort to the guilty, since God “… made him to be sin for us … that we might be made the righteousness of God in him” (2 Corinthians 5:21).
Believe that these things are true; that His sacrifice is complete and fully accepted, so that he that believeth on Jesus is not condemned. Believe the witness of God, just as you believe the testimony of your own father or friend. “If we receive the witness of men, the witness of God is greater … “ (1 John 5:9).
One more ingredient is needed – trust. Rest your hope on the gracious Gospel; trust your soul to the dying and living Saviour. Faith believes that Christ will do what He has promised; that since He has cast out none that came to Him, it is certain that He will not cast us out if we come to Him.
The great matter is to believe on the Lord Jesus Christ at once. There are, no doubt, many at this hour in Hell who understood the doctrine of faith, but did not believe. On the other hand, not one who has trusted the Lord Jesus has ever been cast out. Receive the Lord Jesus into your soul, and you shall live forever! “… He that believeth on me hath everlasting life” (John 6:47).