Faith in the Lord Jesus is the very key of salvation. He that has it has life, and he that has it not has not life. Nothing whatever beside this faith is necessary to our complete justification; but nothing whatever, except this faith, will give us an interest in Christ. We may fast and mourn for sin, and do many things that are right, and use religious ordinances, and give all our goods to feed the poor, and yet remain unpardoned, and lose our souls. But if we will only come to Christ as guilty sinners, and believe on Him, our sins shall at once be forgiven, and our iniquities shall be entirely put away. Without faith there is no salvation; but through faith in Jesus, the vilest sinner may be saved.
~ J.C. Ryle
Expository Thoughts on the Gospels: John, volume 1, [Carlisle, PA: Banner of Truth, 1987], 145, 146.