And it is profitable to the soul, as the Lord says:
He that heareth My words, and believeth Him that sent Me, hath everlasting life, and cometh not into judgment (John 5:24).
And again, He that believeth in the Son is not judged, but hath passed from death unto life (John 3:18; 5:24).
Oh the great loving-kindness of God!
For the righteous were many years in pleasing Him, but what they succeeded in gaining by many years of well-pleasing this Jesus now bestows on you in a single hour.
For if you believe that Jesus Christ is Lord, and that God raised Him from the dead, you will be saved, and will be transported into Paradise by Him who brought in thither the robber.
And doubt not whether it is possible; for He who on this sacred Golgotha saved the robber after one single hour of belief shall save you also because of your believing (Luke 23:43).
But there is a second kind of faith, which is bestowed by Christ as a gift of grace.
For to one is given through the Spirit the word of wisdom, and to another the word of knowledge according to the same Spirit: to another faith, by the same Spirit, and to another gifts of healing (1 Cor. 12:8-9).
This faith, which is given of grace from the Spirit, is not merely doctrinal, but also works things above man’s power. For whosoever has this faith shall say to this mountain, Remove hence to yonder place, and it shall remove (Mark 11:23).
Whenever anyone says this in faith, believing that it will come to pass, and does not doubt in his heart, then he will receive the grace.
And of this faith it is said, If ye have faith as a grain of mustard seed (Matt 17:20).
The grain of mustard seed is small in size, but fiery in its operation, and though sown in a small space has a circle of great branches, and when grown up is able even to shelter the fowls (Matt. 13:32).
Likewise, faith in the swiftest moment works the greatest effects in the soul.
For, enlightened by faith, the soul has visions of God, and as far as is possible beholds God, and ranges round the bounds of the universe, and before the end of this world already beholds the Judgment, and the payment of the promised rewards.
Have, therefore, that faith in Him which comes from your own self, that you may also receive from Him that faith which works things above man.
Cyril of Jerusalem (c. 313-386): Catechetical Lectures 5, 10-11 [slightly adapted].