Who produces the faith? What is involved in hearing?
As stated Paul revealed that faith comes by hearing, and hearing by the Word of God.
"For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart." Heb 4:12
The following commentary conveys the principle far better than could I:
Hebrews 4:12
The "Word of God" is "what God speaks" - whether it be a promise or a threatening; whether it be Law or gospel; whether it be a simple declaration or a statement of a doctrine. The idea here is, that what "God had said" is suited to detect hypocrisy and to lay open the true nature of the feelings of the soul, so that there can be no escape for the guilty. His "truth" is adapted to bring out the real feelings, and to show man exactly what he is. Truth always has this power-whether preached, or read, or communicated by conversation, or impressed upon the memory and conscience by the Holy Spirit. There can be no escape from the penetrating, searching application of the Word of God. That truth has power to show what man is, and is like a penetrating sword that lays open the whole man; compare Isa 49:2. The phrase "the Word of God" here may be applied, therefore, to the "truth" of God, however made known to the mind. In some way it will bring out the real feelings, and show what man is.
[Is quick] Greek zoon - "living."
It is not dead, inert, and powerless. It has a "living" power, and is energetic and active. It is "adapted" to produce this effect.
[And powerful] Mighty. Its power is seen in awakening the conscience; alarming the fears; laying bare the secret feelings of the heart, and causing the sinner to tremble with the apprehension of the coming judgment. All the great changes in the moral world for the better, have been caused by the power of truth. They are such as the truth in its own nature is suited to effect, and if we may judge of its power by the greatness of the revolutions produced, no words can over-estimate the might of the truth which God has revealed.
[Sharper than any two-edged sword] Literally, "two-mouthed" sword - distomon.
The word "mouth" was given to the sword because it seemed to "devour" all before it. It consumed or destroyed as a wild beast does. The comparison of the Word of God to a sword or to an arrow, is designed to show its power of penetrating the heart; Eccl 12:11, "The words of the wise are as goads, and as nails fastened by the masters of assemblies;" compare Isa 49:2. "And he hath made my mouth like a sharp sword;" Rev 1:16, "And out of his mouth went a sharp two-edged sword;" Rev 2:12,16; 19:15. The comparison is common in the classics, and in Arabic poetry; see Gesenius, on Isa 49:2. The idea is that of piercing, or penetrating; and the meaning here is, that the Word of God reaches the "heart" - the very center of action, and lays open the motives and feelings of the man. It was common among the ancients to have a sword with two edges. The Roman sword was commonly made in this manner. The fact that it had two edges made it more easy to penetrate, as well as to cut with every way.
[Piercing even to the dividing asunder] Penetrating so as to divide.[Soul and spirit] The animal life from the immortal soul. The former word here - psuchee - "soul" - is evidently used to denote the "animal life," as distinguished from the mind or soul.
The latter word - pneuma- "spirit" - means the soul; the immaterial and immortal part; what lives when the animal life is extinct. This distinction occurs in 1 Thess 5:23, "your whole spirit, and soul, and body;" and it is a distinction which we are constantly in the habit of making. There is the body in man-the animal life—and the immortal part that leaves the body when life is extinct. Mysteriously united, they constitute one man. When the animal life is separated from the soul, or when the soul leaves the animated body, the body dies, and life is extinct. To separate the one from the other is, therefore, the same as to take life—and this is the idea here, that the Word of God is like a sharp sword that inflicts deadly wounds. The sinner "dies;" that is, he becomes dead to his former hopes, or is "slain" by the Law; Rom 7:9, "I was alive without the law once, but when the commandment came, sin revived, and I died." This is the power referred to here-the power of destroying the hopes of the sinner; cutting him down under conviction; and prostrating him as if a sword had pierced his heart.
[And of the joints and marrow] The figure is still continued of the sword that takes life. Such a sword would seem to penetrate even the joints and marrow of the body. It would separate the joints, and pierce through the very bones to the marrow. A similar effect, Paul says, is produced by truth. It seems to penetrate the very essence of the soul, and lay it all open to the view.
[And is a discerner of the thoughts] It shows what the thoughts and intentions are. Prof. Stuart, Bloomfield, and some others, suppose that the reference here is to "God" speaking by his word. But the more natural construction certainly is, to refer it to the Word or truth of God. It is true that God searches the heart, and knows the thoughts, but that is not the truth which is prominent here. It is, that the thoughts and intents of the heart are brought out to view by the Word of God. And can anyone doubt this? see Rom 7:7. Is it not true that people are made to see their real character under the exhibition of the truth of God? That in the light of the Law they see their past lives to be sinful? That the exhibition of truth calls to their recollection many long-forgotten sins? And that their real feelings are brought out when the truth of God is proclaimed? Men then are made to look upon their motives as they had never done before, and to see in their hearts feelings whose existence they would not have suspected if it had not been for the exhibition of the truth. The exhibition of the truth is like pouring down the beams of the sun at midnight on a dark world; and the truth lays open the real feelings of the sinner as that sun would disclose the clouds of wickedness that are now performed under cover of the night. Many a man has a deep and fixed hostility to God and to his gospel who might never be sensible of it if the truth was not faithfully proclaimed. The particular idea here is, that the truth of God will detect the feelings of the hypocrite and self-deceiver. They cannot always conceal their emotions, and the time will come when truth, like light poured into the soul, will reveal their unbelief and their secret sins. They who are cherishing a hope of salvation, therefore, should be on their guard lest they mistake the name for the reality.
Let us learn from this verse:
(1) The power of truth. It is "suited" to lay open the secret feelings of the soul. There is not an effect produced in awakening a sinner; or in his conviction, conversion, and sanctification, which the truth is not "adapted" to produce. The truth of God is not dead; nor suited to make people "worse;" nor designed merely to show its own "weakness," and to be a mere occasion on which the Holy Spirit acts on the mind; it is in its own nature FITTED to produce just the effects which are produced when it awakens, convicts, converts, and sanctifies the soul.
(2) The truth should be preached with the feeling that it is adapted to this end...
(from Barnes' Notes, Electronic Database Copyright © 1997, 2003, 2005, 2006 by Biblesoft, Inc. All rights reserved.)