"Believe on the Lord Jesus Christ and thou shalt be saved." Ah, but what is it to believe? One must have faith in Him. But what is faith?
Saving faith consists in your believing that Jesus Christ came to save the lost, acknowledging yourself as a lost creature, you appropriate, or take hold of Him, as your own personal Savior. In your helplessness, your dependence is entirely upon the faithfulness of God not to disappoint you. It is belief of the good news; acceptance of Jesus as your Savior, and of complete salvation in Him, and a firm trust in God that He will fulfill all His promises. It is not trusting to services, ceremonies, or sacraments, but it is coming to the Lord Jesus and saying, "Lord, Thou didst come to seek and to save the lost. I know that Thou art able and willing to save me. I therefore put myself, soul and body, into Thy hands to save me now, from the power of sin here, and the punishment of sin hereafter. Lord, I take Thee as my Savior; O my God, I trust Thee to the uttermost."
This is saving faith. In other words, saving faith believes the gospel history or record; appropriates, or makes its own, the gospel offer; and trusts God for its complete fulfillment.