The Demonstrations begin
17 Also our Saviour used thus to say to every one who drew near to Him to be healed:— According to your faith be unto you. And when the blind man approached Him, He said to him:— Do you believe that I am able to heal you? That blind man said to Him:— Yea, Lord, I believe. And his faith opened his eyes. And to him whose son was sick, He said:— Believe and your son shall live. He said to Him:— I believe, Lord; help my feeble faith. And by his faith his son was healed. And also when the nobleman came near to Him, by his faith was his boy healed, when he said to our Lord:— Speak the word and my servant will be cured. And our Lord was astonished at his faith, and according to his faith it happened to him. And also when the chief of the Synagogue requested Him concerning his daughter, He said thus to him:— Only firmly believe and your daughter shall live. So he believed and his daughter lived and arose. And when Lazarus died, our Lord said to Martha:— If you believe, your brother shall rise. Martha says unto Him— Yea, Lord, I believe. And He raised him after four days. And also Simon who was called Cephas because of his faith was called the firm rock. And again when our Lord gave the Sacrament of Baptism to His apostles, He said thus to them:— Whosoever believes and is baptized shall live, and whosoever believes not shall be condemned. Again He said to his Apostles:— If you believe and doubt not, there is nothing you shall not be able to do. For when our Lord walked on the billows of the sea, Simon also by his faith walked with Him; but when in respect of his faith he doubted, and began to sink, our Lord called him, you of little faith. And when the Apostles asked of our Lord, they begged nothing at His hands but this, saying to Him:— Increase our faith. He said to them:— If there were in you faith, even a mountain would remove from before you. And He said to them:— Doubt not, lest you sink down in the midst of the world, even as Simon when he doubted began to sink in the midst of the sea. And again He said thus— This shall be the sign for those that believe; they shall speak with new tongues and shall cast out demons, and they shall lay their hands on the sick and they shall be made whole.
18. Let us draw near then, my beloved, to faith, since its powers are so many. For faith raised up to the heavens (Enoch), and conquered the Deluge. It caused the barren to bring forth. It delivered from the sword. It raised up from the pit. It enriched the poor. It released the captives. It delivered the persecuted. It brought down the fire. It divided the sea. It cleft the rock, and gave to the thirsty water to drink. It satisfied the hungry. It raised the dead, and brought them up from Sheol. It stilled the billows. It healed the sick. It conquered hosts. It overthrew walls. It stopped the mouths of lions, and quenched the flame of fire. It humiliated the proud, and brought the humble to honour. All these mighty works were wrought by faith.
19. Now thus is faith; when a man believes in God the Lord of all, Who made the heavens and the earth and the seas and all that is in them; and He made Adam in His image; and He gave the Law to Moses; He sent of His Spirit upon the prophets; He sent moreover His Christ into the world. Furthermore that a man should believe in the resurrection of the dead; and should furthermore also believe in the sacrament of baptism. This is the faith of the Church of God. And (it is necessary) that a man should separate himself from the observance of hours and Sabbaths and moons and seasons, and divinations and sorceries and Chaldæan arts and magic, from fornication and from festive music, from vain doctrines, which are instruments of the Evil One, from the blandishment of honeyed words, from blasphemy and from adultery. And that a man should not bear false witness, and that a man should not speak with double tongue. These then are the works of the faith which is based on the true Stone which is Christ, on Whom the whole building is reared up.
20. Furthermore, my beloved, there is much besides in the Holy Books about faith. But these few things out of the much have I written to recall them to your love that you may know and make known and believe and also be believed. And when you have read and learned the works of faith, you may be made like that tilled land upon which the good seed fell, and produced fruit a hundred-fold and sixty-fold and thirty-fold. And when you come to your Lord, He may call you a good servant and prudent and faithful, who on account of His faith, that abounded, is to enter into the Kingdom of his Lord.
Source: Demonstrations (New Advent)